strcat返回错误的字符

Question

I am using strcat to build a string. It works except for when I want to append characters that represent numbers from an array. The line that uses:

strcat(JsonDataStr, numsToSend[i]);

for example appends the character 'c' instead of '1'. If I manually put the character in using double quotes it works, but i want to have a one dimensional array with characters only.

char JsonDataStr[20];

void buildJsonString(){

    int offset;
    char strtStr[] = "[{\""  ;
    char numStr[4];
    char numsToSend[4] = {'1', '2','3','4'};

    offset = sizeof(strtStr);

    strcat(JsonDataStr, strtStr);

    for(i = 0 ; i < 2 ; i++){
           strcat(JsonDataStr, JsonDataName);
           ByteToStr(i, numStr);
           strcat(JsonDataStr, numsToSend[i]);
           strcat(JsonDataStr, "\":\"");
    }
    strcat(JsonDataStr, "\"}]");
}

Any idea why this is happening.

Answer 1

You can't use strcat like this. It appends strings to strings, not single chars to strings. A quick fix would be to have numsToSend as an array of char pointers instead:

char *numsToSend[4] = { "1", "2", "3", "4" };

Other than that you could write a function that appends chars to strings, see this answer for an example.