Message sends in Objective-C

Square brackets everywhere — and nil quietly absorbs messages.

#import <Foundation/Foundation.h>

int main(void) {
    @autoreleasepool {
        // Everything happens by sending messages in square brackets.
        NSString *title = @"blue train";

        // Sends nest inside sends, reading inside out.
        NSString *display = [[title uppercaseString]
            stringByAppendingString:@" [remastered]"];
        NSLog(@"%@", display);

        // A message to nil quietly answers zero -- no crash.
        NSString *missing = nil;
        NSLog(@"Missing length: %lu", (unsigned long)[missing length]);
    }
    return 0;
}

How it works

1. [title uppercaseString] sends a message to an object.
2. Sends nest: the inner result receives the outer message.
3. Messaging nil returns zero instead of crashing — a defining quirk.

Keywords and builtins used here

• NSString
• int
• long
• main
• nil
• return
• unsigned
• void

The run, in numbers

Lines

18

Characters to type

483

Tokens

75

Three-star pace

65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 69 seconds.

Type this snippet

Step 1 of 3 in Messages, step 4 of 27 in Language basics.

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