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65 lines
1.4 KiB
Markdown
65 lines
1.4 KiB
Markdown
# nlohmann::json_pointer::front
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```
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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](https://json.nlohmann.me/home/exceptions/#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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```
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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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// 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() << "\"" << std::endl;
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}
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```
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Output:
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```
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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](https://json.nlohmann.me/api/json_pointer/back/index.md) return last reference token
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- [pop_front](https://json.nlohmann.me/api/json_pointer/pop_front/index.md) remove the first reference token
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- [push_front](https://json.nlohmann.me/api/json_pointer/push_front/index.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 unreleased.
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