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nlohmann
78 lines
2.3 KiB
Markdown
78 lines
2.3 KiB
Markdown
# nlohmann::basic_json::array
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```
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static basic_json array(initializer_list_t init = {});
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```
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Creates a JSON array value from a given initializer list. That is, given a list of values `a, b, c`, creates the JSON value `[a, b, c]`. If the initializer list is empty, the empty array `[]` is created.
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## Parameters
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`init` (in) : initializer list with JSON values to create an array from (optional)
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## Return value
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JSON array value
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## Exception safety
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Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
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## Complexity
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Linear in the size of `init`.
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## Notes
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This function is only needed to express two edge cases that cannot be realized with the initializer list constructor ([`basic_json(initializer_list_t, bool, value_t)`](https://json.nlohmann.me/api/basic_json/basic_json/index.md)). These cases are:
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1. creating an array whose elements are all pairs whose first element is a string -- in this case, the initializer list constructor would create an object, taking the first elements as keys
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1. creating an empty array -- passing the empty initializer list to the initializer list constructor yields an empty object
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## Examples
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Example
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The following code shows an example for the `array` function.
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```
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#include <iostream>
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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int main()
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{
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// create JSON arrays
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json j_no_init_list = json::array();
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json j_empty_init_list = json::array({});
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json j_nonempty_init_list = json::array({1, 2, 3, 4});
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json j_list_of_pairs = json::array({ {"one", 1}, {"two", 2} });
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// serialize the JSON arrays
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std::cout << j_no_init_list << '\n';
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std::cout << j_empty_init_list << '\n';
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std::cout << j_nonempty_init_list << '\n';
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std::cout << j_list_of_pairs << '\n';
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}
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```
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Output:
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```
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[]
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[]
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[1,2,3,4]
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[["one",1],["two",2]]
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```
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## See also
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- [`basic_json(initializer_list_t)`](https://json.nlohmann.me/api/basic_json/basic_json/index.md) - create a JSON value from an initializer list
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- [`object`](https://json.nlohmann.me/api/basic_json/object/index.md) - create a JSON object value from an initializer list
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- [Creating JSON values](https://json.nlohmann.me/features/creating_values/index.md) - the article on creating JSON values
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## Version history
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- Added in version 1.0.0.
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