NSData appendBytes, adding string

Question

I'm trying to create a NSData depending on a switch, but I'm having trouble adding the options to the method appendBytes. Adding the NSString test gives me an error.

Example:

- (void)selectCenterJustification:(int)option
{
    NSMutableData *data;
    NSString *test;
    switch (option)
    {
        case 0:
            test = @"\x0";
            break;
        case 1:
            test = @"\x1";
            break;
        case 2:
            test = @"\x2";
            break;
    }
    // does not work because of "test"
    [data appendBytes:"\x1b" "a", test length:3];

    // working
    [data appendBytes:"\x1b" "a" "\x1" length:3];
}

Any idea how I can do this?

Gerdinando · Accepted Answer · 2013-08-14 13:35:29Z

3

NSMutableData *data = [NSmutableData data];
NSString *test = nil;

switch (option) {
    case 0:
        test = @"\x0";
        break;
    case 1:
        test = @"\x1";
        break;
    case 2:
        test = @"\x2";
        break;
    default:
        NSLog(@"[justification]: unknown option");
        break;
}
if (test) {
    [data appendBytes:"\x1b" "a" length:2];
    [data appendBytes:[test cStringUsingEncoding:NSASCIIStringEncoding] length:1];
}

Update

It appears you need C strings.

edited Aug 14, 2013 at 13:35

Gerdinando

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answered Aug 14, 2013 at 12:54

sbarow

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8 Comments

Matthias Bauch Over a year ago

make sure to alloc-init data before trying to append to it

Gerdinando Over a year ago

Problem isn't appending test, but to add it together with the other data. (see edit in original post)

sbarow Over a year ago

What do you mean add it together with other data? If I understand correctly you should be creating an instance variable to append data too as opposed to create a local variable of NSMutableData.

Gerdinando Over a year ago

Originally data is an instance variable. I just changed it to local so the example will work after copying it :).

sbarow Over a year ago

Okay updated my answer to use NSMutableString which you can append to then convert to NSData. Hope I understood correctly.

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