Fast enumeration in Objective-C

for-in walks arrays in order and dictionaries by key.

#import <Foundation/Foundation.h>

int main(void) {
    @autoreleasepool {
        NSArray<NSString *> *queue =
            @[ @"clean sleeve", @"grade vinyl", @"price", @"shelve" ];
        // for-in walks any collection in order.
        NSInteger step = 1;
        for (NSString *task in queue) {
            NSLog(@"%ld. %@", (long)step, task);
            step += 1;
        }
        // Dictionaries enumerate their keys.
        NSDictionary *graded = @{ @"VG+" : @12, @"NM" : @5 };
        for (NSString *grade in graded) {
            NSLog(@"%@: %@ records", grade, graded[grade]);
        }
    }
    return 0;
}

How it works

for (NSString *task in queue) needs no index bookkeeping.
A counter travels alongside when position matters.
Enumerating a dictionary yields its keys; subscript for values.

Keywords and builtins used here

NSArray
NSDictionary
NSString
for
in
int
long
main
return
void

The run, in numbers

Lines: 20
Characters to type: 491
Tokens: 121
Three-star pace: 65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 112 seconds.

Type this snippet

Step 1 of 3 in Enumeration, step 13 of 27 in Language basics.

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