nlohmann::json obj1, obj2, obj3, obj4;
const
char
* p =
"
{\"age\":22,\"gender\":true,\"name\":\"jack\",\"pet\":{\"name\":\"wang\",\"type\":\"dog\"}}
"
;
std::istringstream ostr(
"
{\"age\":45,\"gender\":true,\"name\":\"skipper\",\"pet\":{\"name\":\"wang\",\"type\":\"dog\"}}
"
);
//
示例json
//
{"age":22,"family":[{"call":"father","name":"adam"},{"call":"mother","name":"eve"},
{"call":"wife","name":"shine"}],"gender":true,"name":"jack","pet":{"name":"wang","type":"dog"}}
//
a.赋值构造
obj1[
"
name
"
] =
"
jack
"
;
//
字符串
obj1[
"
age
"
] =
22
;
//
整数
obj1[
"
gender
"
] =
true
;
//
布尔值
obj1[
"
pet
"
] = { {
"
type
"
,
"
dog
"
}, {
"
name
"
,
"
wang
"
} };
//
对象
知识补充:
nlohmann::json 中的数组是用{}，而不是[]
obj1[
"
family
"
] = { {{
"
call
"
,
"
father
"
}, {
"
name
"
,
"
adam
"
}},{{
"
call
"
,
"
mother
"
}, {
"
name
"
,
"
eve
"
}} };
//
数组
obj1[
"
family
"
][
2
] = { {
"
call
"
,
"
wife
"
}, {
"
name
"
,
"
shine
"
} };
//
元素赋值
//
b.直接构造
obj2 = { {
"
type
"
,
"
dog
"
}, {
"
name
"
,
"
wang
"
} };
//
c.字符串构造
知识补充:
注意nlohmann::json::parse()函数签名
nlohmann::json::parse(const char*, const char*)
obj3 = nlohmann::json::parse(p, p +
strlen(p));
//
d.字符流构造(也可以使用std::ifstream之类替换)
ostr >>
obj4;
//
属性提取
void
test2()
nlohmann::json tmp;
const
char
* p =
"
{\"age\":22,\"gender\":true,\"name\":\"jack\",\"pet\":{\"name\":\"wang\",\"type\":\"dog\"}}
"
;
nlohmann::json obj
= nlohmann::json::parse(p, p +
strlen(p));
//
nlohmann::json为空判断(不可以使用NULL)
if
(nullptr ==
tmp)
std::cout
<<
"
empty
"
<<
std::endl;
//
提取字符串
std::
string
name = obj[
"
name
"
].
get
<std::
string
>
();
//
提取整型
int
age = obj[
"
age
"
].
get
<
int
>
();
//
提取布尔值
bool
gender = obj[
"
gender
"
].
get
<
bool
>
();
//
提取对象
nlohmann::json pet = obj[
"
pet
"
];
std::cout
<< name <<
"
:
"
<< age <<
"
:
"
<< gender <<
std::endl;
//
数组遍历
void
test3()
const
char
* p =
"
[{\"name\":\"1\",\"type\":\"a\"},{\"name\":\"2\",\"type\":\"b\"},
{\"name\":\"c\",\"type\":\"a\"},{\"name\":\"4\",\"type\":\"d\"}]
"
;
nlohmann::json obj;
obj
= nlohmann::json::parse(p, p +
strlen(p));
if
(obj.empty())
//
数组为空
std::cout <<
"
The array is empty
"
<<
std::endl;
return
;
//
遍历数组
for
(auto&
item : obj.items())
//
item.value() = {"name":"1","type":"a"}
std::cout << item.value() <<
std::endl;
int
main()
//
test1();
//
test2();
test3();
return
0
;
https://github.com/nlohmann/json
