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### jsoncons::jsonpath::replace
```cpp
#include <jsoncons_ext/jsonpath/jsonpath.hpp>
template <typename Json>
std::pair<Json*,bool> replace(Json& root,
const basic_json_location<Json::char_type>& location,
const Json& new_value,
bool create_if_missing=false)
```
Replace a JSON value in a JSON document at a specified location.
If `create_if_missing` is `false`, the target location must exist
for the replacement to succeed. If `create_if_missing` is `true`,
and if the target location specifies object members that do not
already exist, the missing objects and members are added.
#### Parameters
<table>
<tr>
<td>root</td>
<td>Root JSON value</td>
</tr>
<tr>
<td>location</td>
<td>A <a href="basic_json_location.md">basic_json_location</a></td>
</tr>
<tr>
<td>new_value</td>
<td>Replacement value</td>
</tr>
<tr>
<td><code>create_if_missing</code></td>
<td>Create key-object pairs when object key is missing</td>
</tr>
</table>
#### Return value
Returns a `std::pair<Json*,bool>`. If the replacement succeeded, the bool component is `true`, and
the `Json*` component points to the new value in the `root`. If the replacement failed, the bool component is `false`.
#### Exceptions
None
### Examples
```cpp
#include <jsoncons/json.hpp>
#include <jsoncons_ext/jsonpath/jsonpath.hpp>
#include <cassert>
#include <iostream>
using jsoncons::json;
namespace jsonpath = jsoncons::jsonpath;
int main()
{
std::string json_string = R"(
{"books": [
{ "category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{ "category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour"
},
{ "category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3"
}
]
}
)";
json doc = json::parse(json_string);
json new_value{13.0};
jsonpath::json_location loc0 = jsonpath::json_location::parse("$.books[0].price");
auto result0 = jsonpath::replace(doc, loc0, new_value);
assert(result0.second);
assert(result0.first == std::addressof(doc.at("books").at(0).at("price")));
assert(doc.at("books").at(0).at("price") == new_value);
jsonpath::json_location loc1 = jsonpath::json_location::parse("$.books[1].price");
auto result1 = jsonpath::replace(doc, loc1, new_value);
assert(!result1.second);
// create_if_missing is true
result1 = jsonpath::replace(doc, loc1, new_value, true);
assert(result1.second);
assert(result1.first == std::addressof(doc.at("books").at(1).at("price")));
assert(doc.at("books").at(1).at("price") == new_value);
jsonpath::json_location loc2 = jsonpath::json_location::parse("$.books[2].kindle.price");
auto result2 = jsonpath::replace(doc, loc2, new_value, true);
assert(result2.second);
assert(result2.first == std::addressof(doc.at("books").at(2).at("kindle").at("price")));
assert(doc.at("books").at(2).at("kindle").at("price") == new_value);
std::cout << pretty_print(doc) << "\n\n";
}
```
Output:
```json
{
"books": [
{
"author": "Nigel Rees",
"category": "reference",
"price": 13.0,
"title": "Sayings of the Century"
},
{
"author": "Evelyn Waugh",
"category": "fiction",
"price": 13.0,
"title": "Sword of Honour"
},
{
"author": "Herman Melville",
"category": "fiction",
"isbn": "0-553-21311-3",
"kindle": {
"price": 13.0
},
"title": "Moby Dick"
}
]
}
```
|
