c操作json数据

1、json库下载

GitHub - DaveGamble/cJSON: Ultralightweight JSON parser in ANSI C

cmake .编译、 make编译，保留cJSON.h和libcjson.a文件

项目CMakeLists.txt引入：

include_directories("/Users/sumengnan/CLionProjects/testc/include")
link_directories("/Users/sumengnan/CLionProjects/testc/lib")
target_link_libraries(testc libcjson.a)

2、json对象转字符串

#include "cJSON.h"
    //json转字串
    //1、创建JSONObject
    cJSON *root = cJSON_CreateObject();
    //相似的创建json对象还有如下……
//    cJSON_CreateArray();
//    cJSON_CreateNull();
//    cJSON_CreateString();
//    cJSON_CreateNumber();

    //2、创建子object
    //创建json string对象
    cJSON_AddItemToObject(root,"username", cJSON_CreateString("sumengnan"));
    cJSON_AddStringToObject(root,"pass","123456");
    //创建json数组对象
    cJSON *array = cJSON_CreateArray();
    cJSON_AddItemToArray(array, cJSON_CreateString("a"));
    cJSON_AddItemToArray(array, cJSON_CreateString("b"));
    cJSON_AddItemToArray(array, cJSON_CreateString("c"));
    cJSON_AddItemToObject(root,"letter",array);

    char *string = cJSON_Print(root);
    printf("%s\n",string);
    //释放内存
    cJSON_Delete(root);

执行结果：

{

"username": "sumengnan",

"pass": "123456",

"letter": ["a", "b", "c"]

}

3、字符串转json对象

char *a="{\"errNo\":\"403\",\"data\": { \"redDot\": [ \"a\",\"b\",\"c\"  ], \"newWord\": [  ], \"layer\": [  ] }}";
cJSON *root = cJSON_Parse(a);
//获取errNo对象
cJSON *errNoJson = cJSON_GetObjectItem(root, "errNo");
printf("errNoJson:%s\n",cJSON_GetStringValue(errNoJson));

//获取data->redDot数组对象
cJSON *dataJson = cJSON_GetObjectItem(root, "data");
cJSON *redDotJson = cJSON_GetObjectItem(dataJson, "redDot");
for(int i=0;i<cJSON_GetArraySize(redDotJson);i++){
    cJSON *redDotItemJson = cJSON_GetArrayItem(redDotJson, i);
    printf("redDotJson:%d:%s\n",i, cJSON_GetStringValue(redDotItemJson));
}

执行结果：

errNoJson:403

redDotJson:0:a

redDotJson:1:b

redDotJson:2:c