Question

I’m looking to use the Zimt library and the ZTWebSocket class has a ‘send’ method that accepts NSString with this signature:

- (void)send:(NSString *)message;

I want to send along data as a UTF8 string but the method only accepts regular NSString. What should I do to avoid the compiler warning? Can I cast from UTF8 to regular string without any problems?

websocket = [[ZTWebSocket alloc] ...];

// 1) this will also generate a warning about incompatible pointer type for the arguments
[websocket send:[message UTF8String]];

// 2) what happens during transmission if I cast this back to a regular string? 
[websocket send:(NSString *)[message UTF8String]];

Answer 1

You can’t use -UTF8String since that returns a standard C const char *, not a NSString.

The framework you’re using would need to expose a method for changing the encoding, since it must get the bytes from the string at some point using some encoding (unless it uses a deprecated method that doesn’t specify the encoding).

In short, speak to the guys who make the framework and ask their advice 😉

EDIT | I just looked at the source on github.com, and it’s actually hard-coded to use UTF8, so you’re ok.

Excerpt:

-(void)send:(NSString*)message {
    NSMutableData* data = [NSMutableData data];
    [data appendBytes:"\x00" length:1];
    [data appendData:[message dataUsingEncoding:NSUTF8StringEncoding]];
    [data appendBytes:"\xFF" length:1];
    [socket writeData:data withTimeout:-1 tag:ZTWebSocketTagMessage];
}