I am trying to use C functions in Swift. To do that, I use an Objective-C wrapper. I am not familiar with Objective-C and C so much.

My wrapper function takes Swift String as a parameter from textField. And inside of C I encrypt the passed string and return it.

Here is my C function:

string StringModifier::encryptString(string str) {
    int i;
    for(i=0; (i<100 && str[i] != '\n'); i  ) {
        str[i] = str[i]   2;
    }
    return str;
}

And inside of the wrapper:

StringModifier stringModifier;

-(NSString*)encryptString:(NSString*)str; {
    string strng = [str UTF8String];
    string finalString = stringModifier.encryptString(strng);
    NSString *result = [NSString stringWithCString: finalString.c_str() encoding:[NSString defaultCStringEncoding]];
    return result;
}

The output of encryptString("Helloworld") is "Jgnnqyqtnf¬√√0*?" and after a couple of times calling this method, it throws an EXC_BAD_ACCESS error.

How can I solve this problem?

CodePudding user response：

You need to check for the null character (\0) in C .

Change your for-loop to this:

for(i=0; (i<100 && str[i] != '\n' && str[i] != '\0'); i  ) {
    str[i] = str[i]   2;
}

Even better, loop depending on how big the string is:

string StringModifier::encryptString(string str) {
    for (int i = 0; i < str.size() && str[i] != '\n'; i  ) {
        str[i] = str[i]   2;
    }
    return str;
}