nsstring and const char* conversion

Question

i try to convert nsstring to const char*.

1- i add a nsstring and an integer together
2- then i convert this new nsstring to const char*
3- i have an object and i attribute this new nsstring as my object's name.
4- i use this object in another function

NSString* firstName = [NSString stringWithFormat: @"Name%d", 1];
const char* secondName = [firstName cString];
myobject->setName(secondName);

problem : A
1- secondName is null when i use my object in my function.
2- but if i replace firstName by : firstName = "Name1";
3- it works

problem B
1- if i replace const char* secondName = [firstName cString];
by const char* secondName = [macString UTF8String];
2- even if i have firstName = "Name1";
3- this is not working !!

any idea ??

thank you

:=)

Answer 1

Use cStringUsingEncoding from the NSString class:

NSString *myString = @"Hello";
const char *cString = [myString cStringUsingEncoding:NSASCIIStringEncoding];

Answer 2

const char* are constant, you can't assign them in anyway !

Try passing (const char*)[firstName UTF8String] to your method

Answer 3

NSString* firstName = [NSString stringWithFormat: @"Name%d", 1];

const char* secondName = [firstName UTF8String];

UTF8String returns a const char:   - (const char *)UTF8String

Answer 4

Use this method:

char* MakeStringCopy (const char* string)
{
    if (string == NULL)
        return NULL;

    char* res = (char*)malloc(strlen(string) + 1);
    strcpy(res, string);
    return res;
}

NSString *filePath = @"~/Documents/Image.png";
MakeStringCopy([filePath UTF8String]);