67 lines
1.4 KiB
Markdown
67 lines
1.4 KiB
Markdown
# <small>nlohmann::json_pointer::</small>front
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```cpp
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const string_t& front() const;
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```
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Return the first reference token.
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## Return value
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First reference token.
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## Exception safety
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Strong exception safety: if an exception occurs, the original value stays intact.
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## Exceptions
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Throws [out_of_range.405](../../home/exceptions.md#jsonexceptionout_of_range405) if the JSON pointer has no parent.
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## Complexity
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Constant.
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## Examples
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??? example
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The example shows the usage of `front`.
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```cpp
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#include <iostream>
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#include <nlohmann/json.hpp>
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using nlohmann::json;
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int main()
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{
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// different JSON Pointers
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json::json_pointer ptr1("/foo");
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json::json_pointer ptr2("/foo/0");
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// call empty()
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std::cout << "first reference token of \"" << ptr1 << "\" is \"" << ptr1.front() << "\"\n"
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<< "first reference token of \"" << ptr2 << "\" is \"" << ptr2.front() << "\"" << '\n';
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}
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```
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Output:
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```json
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first reference token of "/foo" is "foo"
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first reference token of "/foo/0" is "foo"
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```
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## See also
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- [`back`](back.md) - return last reference token
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- [`pop_front`](pop_front.md) - remove the first reference token
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- [`push_front`](push_front.md) - append an unescaped token at the start of the pointer
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## Version history
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- Added in version 3.13.0.
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