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2026-10-03 05:43:12 +00:00
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api/basic_json/get_to/index.md
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@@ -7,7 +7,7 @@ ValueType& get_to(ValueType& v) const noexcept(
std::declval<const basic_json_t&>(), v)));
```
Explicit type conversion between the JSON value and a compatible value. The value is filled into the input parameter by calling the `json_serializer<ValueType>` `from_json()` method.
Explicit type conversion between the JSON value and a compatible value. The value is filled into the input parameter by calling the [`json_serializer<ValueType>`](https://json.nlohmann.me/api/basic_json/json_serializer/index.md) `from_json()` method.
The function is equivalent to executing
@@ -31,6 +31,10 @@ This overload is chosen if:
the input parameter, allowing chaining calls
## Exception safety
Depends on what `json_serializer<ValueType>` `from_json()` method throws; the JSON value itself is never modified, since `get_to()` is a `const` member function.
## Exceptions
Depends on what `json_serializer<ValueType>` `from_json()` method throws
@@ -43,11 +47,11 @@ Depends on the `json_serializer<ValueType>::from_json()` implementation.
Example
The example below shows several conversions from JSON values to other types. There a few things to note: (1) Floating-point numbers can be converted to integers, (2) A JSON array can be converted to a standard `std::vector<short>`, (3) A JSON object can be converted to C++ associative containers such as `#cpp std::unordered_map<std::string, json>`.
The example below shows several conversions from JSON values to other types. There a few things to note: (1) Floating-point numbers can be converted to integers, (2) A JSON array can be converted to a standard `std::vector<short>`, (3) A JSON object can be converted to C++ associative containers such as `std::map<std::string, json>`.
```
#include <iostream>
#include <unordered_map>
#include <map>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
@@ -76,7 +80,7 @@ int main()
int v5;
std::string v6;
std::vector<short> v7;
std::unordered_map<std::string, json> v8;
std::map<std::string, json> v8;
// use explicit conversions
json_types["boolean"].get_to(v1);
@@ -116,11 +120,11 @@ Output:
Hello, world!
1 2 3 4 5
number: {"floating-point":17.23,"integer":42}
null: null
string: "Hello, world!"
boolean: true
array: [1,2,3,4,5]
boolean: true
null: null
number: {"floating-point":17.23,"integer":42}
string: "Hello, world!"
```
## See also
@@ -133,4 +137,4 @@ array: [1,2,3,4,5]
## Version history
- Since version 3.3.0.
- Added a `static_assert` with a clear message for `const` arguments in version 3.13.0.
- Added a `static_assert` with a clear message for `const` arguments in version 3.13.0 unreleased.