json/api/json_pointer/push_front.md

nlohmann::json_pointer::push_front

void push_front(const string_t& token);

void push_front(string_t&& token);

Append an unescaped token at the start of the reference pointer.

Parameters

token (in)

token to add

Exception safety

Basic guarantee: if an exception is thrown (for instance, if copying the reference token fails), the JSON pointer is left in a valid state, but its reference tokens may have changed.

Complexity

Linear in the number of reference tokens in the json_pointer.

Examples

??? example

The example shows the result of `push_front` for different JSON Pointers.
 
```cpp
#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    // create empty JSON Pointer
    json::json_pointer ptr;
    std::cout << "\"" << ptr << "\"\n";

    // call push_front()
    ptr.push_front("foo");
    std::cout << "\"" << ptr << "\"\n";

    ptr.push_front("0");
    std::cout << "\"" << ptr << "\"\n";

    ptr.push_front("bar");
    std::cout << "\"" << ptr << "\"\n";
}

```

Output:

```json
""
"/foo"
"/0/foo"
"/bar/0/foo"

```

See also

• front return first reference token
• pop_front remove the first reference token

Version history

• Added in version 3.13.0.