NSEnumerator performance vs for loop in Cocoa

Question

I know that if you have a loop that modifies the count of the items in the loop, using the NSEnumerator on a set is the best way to make sure your code blows up, however I w

Answer 1

After running the test several times, the result is almost the same. Each measure block runs 10 times consecutively.

The result in my case from the fastest to the slowest:

1. For..in (testPerformanceExample3) (0.006 sec)
2. While (testPerformanceExample4) (0.026 sec)
3. For(;;) (testPerformanceExample1) (0.027 sec)
4. Enumeration block (testPerformanceExample2) (0.067 sec)

The for and while loop is almost the same.

The tmp is an NSArray which contains 1 million objects from 0 to 999999.

- (NSArray *)createArray
{
    self.tmpArray = [NSMutableArray array];
    for (int i = 0; i < 1000000; i++)
    {
        [self.tmpArray addObject:@(i)];
    }
    return self.tmpArray;
}

The whole code:

ViewController.h

#import 

@interface ViewController : UIViewController

@property (strong, nonatomic) NSMutableArray *tmpArray;
- (NSArray *)createArray;

@end

ViewController.m

#import "ViewController.h"

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self createArray];
}

- (NSArray *)createArray
{
    self.tmpArray = [NSMutableArray array];
    for (int i = 0; i < 1000000; i++)
    {
        [self.tmpArray addObject:@(i)];
    }
    return self.tmpArray;
}

@end

MyTestfile.m

#import 
#import 

#import "ViewController.h"

@interface TestCaseXcodeTests : XCTestCase
{
    ViewController *vc;
    NSArray *tmp;
}

@end

@implementation TestCaseXcodeTests

- (void)setUp {
    [super setUp];
    vc = [[ViewController alloc] init];
    tmp = vc.createArray;
}

- (void)testPerformanceExample1
{
    [self measureBlock:^{
        for (int i = 0; i < [tmp count]; i++)
        {
            [tmp objectAtIndex:i];
        }
    }];
}

- (void)testPerformanceExample2
{
    [self measureBlock:^{
        [tmp enumerateObjectsUsingBlock:^(NSNumber *obj, NSUInteger idx, BOOL *stop) {
           obj;
        }];
    }];
}

- (void)testPerformanceExample3
{
    [self measureBlock:^{
        for (NSNumber *num in tmp)
        {
            num;
        }
    }];
}

- (void)testPerformanceExample4
{
    [self measureBlock:^{
        int i = 0;
        while (i < [tmp count])
        {
            [tmp objectAtIndex:i];
            i++;
        }
    }];
}

@end

For more information visit: Apples "About Testing with Xcode"