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<!doctype html> < html lang = en class = no-js > < head > < meta charset = utf-8 > < meta name = viewport content = "width=device-width,initial-scale=1" > < meta name = author content = "Niels Lohmann" > < link href = https://json.nlohmann.me/api/basic_json/push_back/ rel = canonical > < link href = ../patch_inplace/ rel = prev > < link href = ../rbegin/ rel = next > < link rel = icon href = ../../../assets/images/favicon.png > < meta name = generator content = "mkdocs-1.5.3, mkdocs-material-9.4.7" > < title > push_back - JSON for Modern C++< / title > < link rel = stylesheet href = ../../../assets/stylesheets/main.4b4a2bd9.min.css > < link rel = stylesheet href = ../../../assets/stylesheets/palette.356b1318.min.css > < link rel = preconnect href = https://fonts.gstatic.com crossorigin > < link rel = stylesheet href = "https://fonts.googleapis.com/css?family=Roboto:300,300i,400,400i,700,700i%7CJetBrains+Mono:400,400i,700,700i&display=fallback" > < style > : root { --md-text-font : "Roboto" ; --md-code-font : "JetBrains Mono" } < / style > < link rel = stylesheet href = ../../../css/custom.css > < script > _ _md _scope = new URL ( "../../.." , location ) , _ _md _hash = e => [ ... e ] . reduce ( ( e , _ ) => ( e << 5 ) - e + _ . charCodeAt ( 0 ) , 0 ) , _ _md _get = ( e , _ = localStorage , t = _ _md _scope ) => JSON . parse ( _ . getItem ( t . pathname + "." + e ) ) , _ _md _set = ( e , _ , t = localStorage , a = _ _md _scope ) => { try { t . setItem ( a . pathname + "." + e , JSON . stringify ( _ ) ) } catch ( e ) { } } < / script > < / head > < body dir = ltr data-md-color-scheme = default data-md-color-primary = indigo data-md-color-accent = indigo > < script > var palette = _ _md _get ( "__palette" ) ; if ( palette && "object" == typeof palette . color ) for ( var key of Object . keys ( palette . color ) ) document . body . setAttribute ( "data-md-color-" + key , palette . color [ key ] ) < / script > < input class = md-toggle data-md-toggle = drawer type = checkbox id = __drawer autocomplete = off > < input class = md-toggle data-md-toggle = search type = checkbox id = __search autocomplete = off > < label class = md-overlay for = __drawer > < / label > < div data-md-component = skip > < a href = #nlohmannbasic_jsonpush_back class = md-skip > Skip to content < / a > < / div > < div data-md-component = announce > < / div > < header class = md-header data-md-component = header > < nav class = "md-header__inner md-grid" aria-label = Header > < a href = ../../.. title = "JSON for Modern C++" class = "md-header__button md-logo" aria-label = "JSON for Modern C++" data-md-component = logo > < svg xmlns = http://www.w3.org/2000/svg viewbox = "0 0 24 24" > < path d = "M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54Z" / > < / svg > < / a > < label class = "md-header__button md-icon" for = __drawer > < svg xmlns = http://www.w3.org/2000/svg viewbox = "0 0 24 24" > < path d = "M3 6h18v2H3V6m0 5h18v2H3v-2m0 5h18v2H3v-2Z" / > < / svg > < / label > < div class = md-header__title data-md-component = header-title > < div class = md-header__ellipsis > < div class = md-header__topic > < span class = md-ellipsis > JSON for Modern C++ < / span > < / div > < div class = md-header__topic data-md-component = header-topic > < span class = md-ellipsis > push_back < / span > < / div > < / div > < / div > < form class = md-header__option data-md-component = palette > < input class = md-option data-md-color-media = "(prefers-color-scheme: light)" data-md-color-scheme = default data-md-color-primary = indigo data-md-color-accent = indigo aria-label = "Switch to dark mode" type = radio name = __palette id = __palette_1 > < label class = "md-header__button md-icon" title = "Switch to dark mode" for = __palette_2 hidden > < svg xmlns = http://www.w3.org/2000/svg viewbox = "0 0 24 24" > < path d = "M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12 20 8.69Z" / > < / svg > < / label > < input class = md-option data-md-color-media = "(prefers-color-scheme: dark)" data-md-color-scheme = slate data-md-color-primary = indigo data-md-color-accent = indigo aria-label = "Switch to light mode" type = radio name = __palette id = __palette_2 > < label class = "md-header__button md-icon" title = "Switch to light mode" for = __palette_1 hidden > < svg xmlns = http://www.w3.org/2000/svg viewbox = "0 0 24 24" > < path d = "M12 18c- . 89 0-1 . 74- . 2-2 . 5- . 55C11 . 56 16 . 5
< span class = kt > void< / span > < span class = w > < / span > < span class = nf > push_back< / span > < span class = p > (< / span > < span class = n > basic_json< / span > < span class = o > & & < / span > < span class = w > < / span > < span class = n > val< / span > < span class = p > );< / span >
< span class = kt > void< / span > < span class = w > < / span > < span class = nf > push_back< / span > < span class = p > (< / span > < span class = k > const< / span > < span class = w > < / span > < span class = n > basic_json< / span > < span class = o > & < / span > < span class = w > < / span > < span class = n > val< / span > < span class = p > );< / span >
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< span class = c1 > // (2)< / span >
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< span class = kt > void< / span > < span class = w > < / span > < span class = nf > push_back< / span > < span class = p > (< / span > < span class = k > const< / span > < span class = w > < / span > < span class = k > typename< / span > < span class = w > < / span > < span class = nc > object_t< / span > < span class = o > ::< / span > < span class = n > value_type< / span > < span class = o > & < / span > < span class = w > < / span > < span class = n > val< / span > < span class = p > );< / span >
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< span class = c1 > // (3)< / span >
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< span class = kt > void< / span > < span class = w > < / span > < span class = nf > push_back< / span > < span class = p > (< / span > < span class = n > initializer_list_t< / span > < span class = w > < / span > < span class = n > init< / span > < span class = p > );< / span >
< / code > < / pre > < / div > < ol > < li > < p > Appends the given element < code > val< / code > to the end of the JSON array. If the function is called on a JSON null value, an empty array is created before appending < code > val< / code > .< / p > < / li > < li > < p > Inserts the given element < code > val< / code > to the JSON object. If the function is called on a JSON null value, an empty object is created before inserting < code > val< / code > .< / p > < / li > < li > < p > This function allows using < code > push_back< / code > with an initializer list. In case< / p > < ol > < li > the current value is an object,< / li > < li > the initializer list < code > init< / code > contains only two elements, and< / li > < li > the first element of < code > init< / code > is a string,< / li > < / ol > < p > < code > init< / code > is converted into an object element and added using < code > push_back(const typename object_t::value_type& )< / code > . Otherwise, < code > init< / code > is converted to a JSON value and added using < code > push_back(basic_json& & )< / code > .< / p > < / li > < / ol > < h2 id = parameters > Parameters< a class = headerlink href = #parameters title = "Permanent link" > ¶ < / a > < / h2 > < dl > < dt > < code > val< / code > (in)< / dt > < dd > the value to add to the JSON array/object< / dd > < dt > < code > init< / code > (in)< / dt > < dd > an initializer list< / dd > < / dl > < h2 id = exceptions > Exceptions< a class = headerlink href = #exceptions title = "Permanent link" > ¶ < / a > < / h2 > < p > All functions can throw the following exception: - Throws < a href = ../../../home/exceptions/#jsonexceptiontype_error308 > < code > type_error.308< / code > < / a > when called on a type other than JSON array or null; example: < code > "cannot use push_back() with number"< / code > < / p > < h2 id = complexity > Complexity< a class = headerlink href = #complexity title = "Permanent link" > ¶ < / a > < / h2 > < ol > < li > Amortized constant.< / li > < li > Logarithmic in the size of the container, O(log(< code > size()< / code > )).< / li > < li > Linear in the size of the initializer list < code > init< / code > .< / li > < / ol > < h2 id = notes > Notes< a class = headerlink href = #notes title = "Permanent link" > ¶ < / a > < / h2 > < p > (3) This function is required to resolve an ambiguous overload error, because pairs like < code > {"key", "value"}< / code > can be both interpreted as < code > object_t::value_type< / code > or < code > std::initializer_list< basic_json> < / code > , see < a href = https://github.com/nlohmann/json/issues/235 > #235< / a > for more information.< / p > < h2 id = examples > Examples< a class = headerlink href = #examples title = "Permanent link" > ¶ < / a > < / h2 > < details class = example > < summary > Example: (1) add element to array< / summary > < p > The example shows how < code > push_back()< / code > and < code > +=< / code > can be used to add elements to a JSON array. Note how the < code > null< / code > value was silently converted to a JSON array.< / p > < div class = highlight > < pre > < span > < / span > < code > < span class = cp > #include< / span > < span class = w > < / span > < span class = cpf > < iostream> < / span >
< span class = cp > #include< / span > < span class = w > < / span > < span class = cpf > < nlohmann/json.hpp> < / span >
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< span class = k > using< / span > < span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = o > =< / span > < span class = w > < / span > < span class = n > nlohmann< / span > < span class = o > ::< / span > < span class = n > json< / span > < span class = p > ;< / span >
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< span class = kt > int< / span > < span class = w > < / span > < span class = nf > main< / span > < span class = p > ()< / span >
< span class = p > {< / span >
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< span class = w > < / span > < span class = c1 > // create JSON values< / span >
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< span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = n > array< / span > < span class = w > < / span > < span class = o > =< / span > < span class = w > < / span > < span class = p > {< / span > < span class = mi > 1< / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 2< / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 3< / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 4< / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 5< / span > < span class = p > };< / span >
< span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = n > null< / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // print values< / span >
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< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > array< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // add values< / span >
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< span class = w > < / span > < span class = n > array< / span > < span class = p > .< / span > < span class = n > push_back< / span > < span class = p > (< / span > < span class = mi > 6< / span > < span class = p > );< / span >
< span class = w > < / span > < span class = n > array< / span > < span class = w > < / span > < span class = o > +=< / span > < span class = w > < / span > < span class = mi > 7< / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > +=< / span > < span class = w > < / span > < span class = s > " first" < / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > +=< / span > < span class = w > < / span > < span class = s > " second" < / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // print values< / span >
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< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > array< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = p > }< / span >
< / code > < / pre > < / div > < p > Output:< / p > < div class = highlight > < pre > < span > < / span > < code > < span class = p > [< / span > < span class = mi > 1< / span > < span class = p > ,< / span > < span class = mi > 2< / span > < span class = p > ,< / span > < span class = mi > 3< / span > < span class = p > ,< / span > < span class = mi > 4< / span > < span class = p > ,< / span > < span class = mi > 5< / span > < span class = p > ]< / span >
< span class = kc > null< / span >
< span class = p > [< / span > < span class = mi > 1< / span > < span class = p > ,< / span > < span class = mi > 2< / span > < span class = p > ,< / span > < span class = mi > 3< / span > < span class = p > ,< / span > < span class = mi > 4< / span > < span class = p > ,< / span > < span class = mi > 5< / span > < span class = p > ,< / span > < span class = mi > 6< / span > < span class = p > ,< / span > < span class = mi > 7< / span > < span class = p > ]< / span >
< span class = p > [< / span > < span class = s2 > " first" < / span > < span class = p > ,< / span > < span class = s2 > " second" < / span > < span class = p > ]< / span >
< / code > < / pre > < / div > < / details > < details class = example > < summary > Example: (2) add element to object< / summary > < p > The example shows how < code > push_back()< / code > and < code > +=< / code > can be used to add elements to a JSON object. Note how the < code > null< / code > value was silently converted to a JSON object.< / p > < div class = highlight > < pre > < span > < / span > < code > < span class = cp > #include< / span > < span class = w > < / span > < span class = cpf > < iostream> < / span >
< span class = cp > #include< / span > < span class = w > < / span > < span class = cpf > < nlohmann/json.hpp> < / span >
< span class = k > using< / span > < span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = o > =< / span > < span class = w > < / span > < span class = n > nlohmann< / span > < span class = o > ::< / span > < span class = n > json< / span > < span class = p > ;< / span >
< span class = kt > int< / span > < span class = w > < / span > < span class = nf > main< / span > < span class = p > ()< / span >
< span class = p > {< / span >
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< span class = w > < / span > < span class = c1 > // create JSON values< / span >
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< span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > =< / span > < span class = w > < / span > < span class = p > {{< / span > < span class = s > " one" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 1< / span > < span class = p > },< / span > < span class = w > < / span > < span class = p > {< / span > < span class = s > " two" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 2< / span > < span class = p > }};< / span >
< span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = n > null< / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // print values< / span >
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< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // add values< / span >
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< span class = w > < / span > < span class = n > object< / span > < span class = p > .< / span > < span class = n > push_back< / span > < span class = p > (< / span > < span class = n > json< / span > < span class = o > ::< / span > < span class = n > object_t< / span > < span class = o > ::< / span > < span class = n > value_type< / span > < span class = p > (< / span > < span class = s > " three" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 3< / span > < span class = p > ));< / span >
< span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > +=< / span > < span class = w > < / span > < span class = n > json< / span > < span class = o > ::< / span > < span class = n > object_t< / span > < span class = o > ::< / span > < span class = n > value_type< / span > < span class = p > (< / span > < span class = s > " four" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 4< / span > < span class = p > );< / span >
< span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > +=< / span > < span class = w > < / span > < span class = n > json< / span > < span class = o > ::< / span > < span class = n > object_t< / span > < span class = o > ::< / span > < span class = n > value_type< / span > < span class = p > (< / span > < span class = s > " A" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = s > " a" < / span > < span class = p > );< / span >
< span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > +=< / span > < span class = w > < / span > < span class = n > json< / span > < span class = o > ::< / span > < span class = n > object_t< / span > < span class = o > ::< / span > < span class = n > value_type< / span > < span class = p > (< / span > < span class = s > " B" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = s > " b" < / span > < span class = p > );< / span >
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< span class = w > < / span > < span class = c1 > // print values< / span >
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< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = p > }< / span >
< / code > < / pre > < / div > < p > Output:< / p > < div class = highlight > < pre > < span > < / span > < code > < span class = p > {< / span > < span class = nt > " one" < / span > < span class = p > :< / span > < span class = mi > 1< / span > < span class = p > ,< / span > < span class = nt > " two" < / span > < span class = p > :< / span > < span class = mi > 2< / span > < span class = p > }< / span >
< span class = kc > null< / span >
< span class = p > {< / span > < span class = nt > " four" < / span > < span class = p > :< / span > < span class = mi > 4< / span > < span class = p > ,< / span > < span class = nt > " one" < / span > < span class = p > :< / span > < span class = mi > 1< / span > < span class = p > ,< / span > < span class = nt > " three" < / span > < span class = p > :< / span > < span class = mi > 3< / span > < span class = p > ,< / span > < span class = nt > " two" < / span > < span class = p > :< / span > < span class = mi > 2< / span > < span class = p > }< / span >
< span class = p > {< / span > < span class = nt > " A" < / span > < span class = p > :< / span > < span class = s2 > " a" < / span > < span class = p > ,< / span > < span class = nt > " B" < / span > < span class = p > :< / span > < span class = s2 > " b" < / span > < span class = p > }< / span >
< / code > < / pre > < / div > < / details > < details class = example > < summary > Example: (3) add to object from initializer list< / summary > < p > The example shows how initializer lists are treated as objects when possible.< / p > < div class = highlight > < pre > < span > < / span > < code > < span class = cp > #include< / span > < span class = w > < / span > < span class = cpf > < iostream> < / span >
< span class = cp > #include< / span > < span class = w > < / span > < span class = cpf > < nlohmann/json.hpp> < / span >
< span class = k > using< / span > < span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = o > =< / span > < span class = w > < / span > < span class = n > nlohmann< / span > < span class = o > ::< / span > < span class = n > json< / span > < span class = p > ;< / span >
< span class = kt > int< / span > < span class = w > < / span > < span class = nf > main< / span > < span class = p > ()< / span >
< span class = p > {< / span >
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< span class = w > < / span > < span class = c1 > // create JSON values< / span >
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< span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > =< / span > < span class = w > < / span > < span class = p > {{< / span > < span class = s > " one" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 1< / span > < span class = p > },< / span > < span class = w > < / span > < span class = p > {< / span > < span class = s > " two" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 2< / span > < span class = p > }};< / span >
< span class = w > < / span > < span class = n > json< / span > < span class = w > < / span > < span class = n > null< / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // print values< / span >
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< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // add values:< / span >
< span class = w > < / span > < span class = n > object< / span > < span class = p > .< / span > < span class = n > push_back< / span > < span class = p > ({< / span > < span class = s > " three" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 3< / span > < span class = p > });< / span > < span class = w > < / span > < span class = c1 > // object is extended< / span >
< span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > +=< / span > < span class = w > < / span > < span class = p > {< / span > < span class = s > " four" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 4< / span > < span class = p > };< / span > < span class = w > < / span > < span class = c1 > // object is extended< / span >
< span class = w > < / span > < span class = n > null< / span > < span class = p > .< / span > < span class = n > push_back< / span > < span class = p > ({< / span > < span class = s > " five" < / span > < span class = p > ,< / span > < span class = w > < / span > < span class = mi > 5< / span > < span class = p > });< / span > < span class = w > < / span > < span class = c1 > // null is converted to array< / span >
< span class = w > < / span > < span class = c1 > // print values< / span >
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< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > object< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
< span class = w > < / span > < span class = n > std< / span > < span class = o > ::< / span > < span class = n > cout< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = n > null< / span > < span class = w > < / span > < span class = o > < < < / span > < span class = w > < / span > < span class = sc > ' \n' < / span > < span class = p > ;< / span >
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< span class = w > < / span > < span class = c1 > // would throw:< / span >
< span class = w > < / span > < span class = c1 > //object.push_back({1, 2, 3});< / span >
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< span class = p > }< / span >
< / code > < / pre > < / div > < p > Output:< / p > < div class = highlight > < pre > < span > < / span > < code > < span class = p > {< / span > < span class = nt > " one" < / span > < span class = p > :< / span > < span class = mi > 1< / span > < span class = p > ,< / span > < span class = nt > " two" < / span > < span class = p > :< / span > < span class = mi > 2< / span > < span class = p > }< / span >
< span class = kc > null< / span >
< span class = p > {< / span > < span class = nt > " four" < / span > < span class = p > :< / span > < span class = mi > 4< / span > < span class = p > ,< / span > < span class = nt > " one" < / span > < span class = p > :< / span > < span class = mi > 1< / span > < span class = p > ,< / span > < span class = nt > " three" < / span > < span class = p > :< / span > < span class = mi > 3< / span > < span class = p > ,< / span > < span class = nt > " two" < / span > < span class = p > :< / span > < span class = mi > 2< / span > < span class = p > }< / span >
< span class = p > [[< / span > < span class = s2 > " five" < / span > < span class = p > ,< / span > < span class = mi > 5< / span > < span class = p > ]]< / span >
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