Calling a C function from Objective-C with string array

Question

I'm trying to call a simple tutorial C function from Objective-C and I can't figure out how to split up the arguments being passed, which is two strings.

int cFunction(int argc, char **argv)
{
    int i;
    printf("argc = %d\n", argc);
    for (i = 0; i < argc; i++) {
        printf("argv[%d] = \"%s\"\n", i, argv[i]);
    }
    return 0;
}

I've tried cFunction(3, "string1 string2"), cFunction(3, "string1", "string2"), and cFunction(3, args), with args being an NSArray composed of [textField1 stringValue] and [textField2 stringValue]

I get EXC_BAD_ACCESS when trying to printf argv[i]. I've also tried passing 2 as the value of argc.

How should this be called? Thanks

score 3 · Accepted Answer · 2011-07-16 20:19:48Z

3

In this function parameter list, argv is a pointer to a C string array (char **).

Using the Objective-C NSString or NSArray type isn't possible with this function, First, convert each string using -(const char *)cStringUsingEncoding:(NSStringEncoding)encoding;, and store them into a C array of strings.

// myString is "arg1"
// mySecondString is "arg2"
char *cString = [myString
                 cStringUsingEncoding:NSUTF8StringEncoding];
char *cSecondString = [mySecondString
                       cStringUsingEncoding:NSUTF8StringEncoding];
char *myStrings[2] = { cString, cSecondString };
int returnCode = cFunction(2, myStrings);

This should work.

edited Jul 16, 2011 at 20:19

answered Jul 16, 2011 at 19:11

user756245

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7 Comments

Filo Over a year ago

Ah, sorry I forgot I tried that last night. I don't get EXC_BAD_ACCESS when I do that, but the two strings are both being assigned to argv[0] and I'm trying to get them into argv[0] and argv[1]. Or do I just need to have the cFunction split them on whitespace?

user756245 Over a year ago

You could break a string on whitespaces, but in order to pass the function an array of C strings, you will need to reserve spa ce for the array, and store the pointers to each C string into it.

Filo Over a year ago

I'm making my args by appending textField2 to textField1, with a @" " in between, and my cFunction has "textField1string textField2string" in it.

Filo Over a year ago

Ah so you're saying make my NSArray hold the *cStrings instead of the [textField stringValue]s and then pass the NSArray?

user756245 Over a year ago

for example : char * array [4] = {"one", "two", "three", "four"};.

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