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◆ parse() [1/2]
static basic_json nlohmann::basic_json::parse |
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detail::input_adapter && |
i, |
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const parser_callback_t |
cb = nullptr , |
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const bool |
allow_exceptions = true |
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) |
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inlinestatic |
This function reads from a compatible input. Examples are:
- an array of 1-byte values
- strings with character/literal type with size of 1 byte
- input streams
- container with contiguous storage of 1-byte values. Compatible container types include
std::vector , std::string , std::array , std::valarray , and std::initializer_list . Furthermore, C-style arrays can be used with std::begin() /std::end() . User-defined containers can be used as long as they implement random-access iterators and a contiguous storage.
- Precondition
- Each element of the container has a size of 1 byte. Violating this precondition yields undefined behavior. This precondition is enforced with a static assertion.
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The container storage is contiguous. Violating this precondition yields undefined behavior. This precondition is enforced with an assertion.
- Warning
- There is no way to enforce all preconditions at compile-time. If the function is called with a noncompliant container and with assertions switched off, the behavior is undefined and will most likely yield segmentation violation.
- Parameters
-
[in] | i | input to read from |
[in] | cb | a parser callback function of type parser_callback_t which is used to control the deserialization by filtering unwanted values (optional) |
[in] | allow_exceptions | whether to throw exceptions in case of a parse error (optional, true by default) |
- Returns
- deserialized JSON value; in case of a parse error and allow_exceptions set to
false , the return value will be value_t::discarded.
- Exceptions
-
parse_error.101 | if a parse error occurs; example: ""unexpected end of input; expected string literal"" |
parse_error.102 | if to_unicode fails or surrogate error |
parse_error.103 | if to_unicode fails |
- Complexity
- Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the parser callback function cb has a super-linear complexity.
- Note
- A UTF-8 byte order mark is silently ignored.
- Example
- The example below demonstrates the
parse() function reading from an array.
3 #include <nlohmann/json.hpp>
15 "Title": "View from 15th Floor",
17 "Url": "http://www.example.com/image/481989943",
22 "IDs": [116, 943, 234, 38793]
29 std::cout << std::setw(4) << j_complete << "\n\n";
Output (play with this example online): {
"Image": {
"Animated": false,
"Height": 600,
"IDs": [
116,
943,
234,
38793
],
"Thumbnail": {
"Height": 125,
"Url": "http://www.example.com/image/481989943",
"Width": 100
},
"Title": "View from 15th Floor",
"Width": 800
}
}
The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/parse__array__parser_callback_t.cpp -o parse__array__parser_callback_t
- Example
- The example below demonstrates the
parse() function with and without callback function.
3 #include <nlohmann/json.hpp>
15 "Title": "View from 15th Floor",
17 "Url": "http://www.example.com/image/481989943",
22 "IDs": [116, 943, 234, 38793]
29 std::cout << std::setw(4) << j_complete << "\n\n";
36 if (event == json::parse_event_t::key and parsed == json( "Thumbnail"))
48 std::cout << std::setw(4) << j_filtered << '\n';
Output (play with this example online): {
"Image": {
"Animated": false,
"Height": 600,
"IDs": [
116,
943,
234,
38793
],
"Thumbnail": {
"Height": 125,
"Url": "http://www.example.com/image/481989943",
"Width": 100
},
"Title": "View from 15th Floor",
"Width": 800
}
}
{
"Image": {
"Animated": false,
"Height": 600,
"IDs": [
116,
943,
234,
38793
],
"Title": "View from 15th Floor",
"Width": 800
}
}
The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/parse__string__parser_callback_t.cpp -o parse__string__parser_callback_t
- Example
- The example below demonstrates the
parse() function with and without callback function.
4 #include <nlohmann/json.hpp>
16 "Title": "View from 15th Floor",
18 "Url": "http://www.example.com/image/481989943",
23 "IDs": [116, 943, 234, 38793]
34 std::cout << std::setw(4) << j_complete << "\n\n";
41 if (event == json::parse_event_t::key and parsed == json( "Thumbnail"))
57 std::cout << std::setw(4) << j_filtered << '\n';
Output (play with this example online): {
"Image": {
"Animated": false,
"Height": 600,
"IDs": [
116,
943,
234,
38793
],
"Thumbnail": {
"Height": 125,
"Url": "http://www.example.com/image/481989943",
"Width": 100
},
"Title": "View from 15th Floor",
"Width": 800
}
}
{
"Image": {
"Animated": false,
"Height": 600,
"IDs": [
116,
943,
234,
38793
],
"Title": "View from 15th Floor",
"Width": 800
}
}
The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/parse__istream__parser_callback_t.cpp -o parse__istream__parser_callback_t
- Example
- The example below demonstrates the
parse() function reading from a contiguous container.
3 #include <nlohmann/json.hpp>
10 std::vector<uint8_t> text = { '[', '1', ',', '2', ',', '3', ']', '\0'};
14 std::cout << std::setw(4) << j_complete << "\n\n";
Output (play with this example online): [
1,
2,
3
]
The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/parse__contiguouscontainer__parser_callback_t.cpp -o parse__contiguouscontainer__parser_callback_t
- Since
- version 2.0.3 (contiguous containers)
Definition at line 20755 of file json.hpp.
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