Block enumeration in Objective-C

The collection drives; your block rides along with index and stop.

#import <Foundation/Foundation.h>

int main(void) {
    @autoreleasepool {
        NSArray<NSString *> *arrivals =
            @[ @"Ege Bamyasi", @"Marquee Moon", @"Remain in Light" ];

        // The block receives the object, its index, and a stop switch.
        [arrivals enumerateObjectsUsingBlock:
            ^(NSString *title, NSUInteger idx, BOOL *stop) {
                NSLog(@"Bin %lu: %@", (unsigned long)idx, title);
                if ([title isEqualToString:@"Marquee Moon"]) {
                    *stop = YES;
                }
            }];
    }
    return 0;
}

How it works

1. enumerateObjectsUsingBlock: passes object, index, and a stop flag.
2. *stop = YES ends the walk early from inside the block.
3. The block parameter types are spelled right in the call.

Keywords and builtins used here

• BOOL
• NSArray
• NSString
• YES
• if
• int
• long
• main
• return
• unsigned
• void

The run, in numbers

Lines

18

Characters to type

442

Tokens

94

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 94 seconds.

Type this snippet

Step 2 of 3 in Enumeration, step 14 of 27 in Language basics.

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