mach_absolute_time()有一个方便的包装器——它是来自CoreAnimation框架的CACurrentMediaTime()函数。

与NSDate或CFAbsoluteTimeGetCurrent()偏移量不同， mach_absolute_time()和CACurrentMediaTime()基于 主机内部时钟，精确，单原子测量，且不受影响 外部时间参考的更改，例如由时间引起的更改 区域、夏令时或闰秒。

ObjC

#import <QuartzCore/QuartzCore.h>

CFTimeInterval startTime = CACurrentMediaTime();
// Do your stuff here
CFTimeInterval endTime = CACurrentMediaTime();
NSLog(@"Total Runtime: %g s", endTime - startTime);

斯威夫特

import QuartzCore

let startTime = CACurrentMediaTime()
// Do your stuff here
let endTime = CACurrentMediaTime()
print("Total Runtime: \(endTime - startTime) s")

下面是我使用的两个单行宏:

#define TICK   NSDate *startTime = [NSDate date]
#define TOCK   NSLog(@"Time: %f", -[startTime timeIntervalSinceNow])

像这样使用它:

TICK;

/* ... Do Some Work Here ... */

TOCK;

我使用非常少的，一页的类实现，灵感来自这篇博客文章的代码:

#import <mach/mach_time.h>

@interface DBGStopwatch : NSObject

+ (void)start:(NSString *)name;
+ (void)stop:(NSString *)name;

@end

@implementation DBGStopwatch

+ (NSMutableDictionary *)watches {
    static NSMutableDictionary *Watches = nil;
    static dispatch_once_t OnceToken;
    dispatch_once(&OnceToken, ^{
        Watches = @{}.mutableCopy;
    });
    return Watches;
}

+ (double)secondsFromMachTime:(uint64_t)time {
    mach_timebase_info_data_t timebase;
    mach_timebase_info(&timebase);
    return (double)time * (double)timebase.numer /
        (double)timebase.denom / 1e9;
}

+ (void)start:(NSString *)name {
    uint64_t begin = mach_absolute_time();
    self.watches[name] = @(begin);
}

+ (void)stop:(NSString *)name {
    uint64_t end = mach_absolute_time();
    uint64_t begin = [self.watches[name] unsignedLongLongValue];
    DDLogInfo(@"Time taken for %@ %g s",
              name, [self secondsFromMachTime:(end - begin)]);
    [self.watches removeObjectForKey:name];
}

@end

它的用法很简单:

调用[DBGStopwatch start:@"slow-operation"];一开始 然后[DBGStopwatch stop:@"slow-operation"];做完之后，才能得到时间

mach_absolute_time()有一个方便的包装器——它是来自CoreAnimation框架的CACurrentMediaTime()函数。

与NSDate或CFAbsoluteTimeGetCurrent()偏移量不同， mach_absolute_time()和CACurrentMediaTime()基于 主机内部时钟，精确，单原子测量，且不受影响 外部时间参考的更改，例如由时间引起的更改 区域、夏令时或闰秒。

ObjC

#import <QuartzCore/QuartzCore.h>

CFTimeInterval startTime = CACurrentMediaTime();
// Do your stuff here
CFTimeInterval endTime = CACurrentMediaTime();
NSLog(@"Total Runtime: %g s", endTime - startTime);

斯威夫特

import QuartzCore

let startTime = CACurrentMediaTime()
// Do your stuff here
let endTime = CACurrentMediaTime()
print("Total Runtime: \(endTime - startTime) s")

这里有另一种方法，在Swift中，使用defer关键字来做到这一点

func methodName() {
  let methodStart = Date()
  defer {
    let executionTime = Date().timeIntervalSince(methodStart)
    print("Execution time: \(executionTime)")
  }
  // do your stuff here
}

来自苹果的文档:defer语句用于在将程序控制权转移到该defer语句出现的范围之外之前执行代码。

这类似于try/finally块，优点是将相关代码分组。

NSDate *methodStart = [NSDate date];

/* ... Do whatever you need to do ... */

NSDate *methodFinish = [NSDate date];
NSTimeInterval executionTime = [methodFinish timeIntervalSinceDate:methodStart];
NSLog(@"executionTime = %f", executionTime);

迅速:

let methodStart = NSDate()

/* ... Do whatever you need to do ... */

let methodFinish = NSDate()
let executionTime = methodFinish.timeIntervalSinceDate(methodStart)
print("Execution time: \(executionTime)")

Swift3:

let methodStart = Date()

/* ... Do whatever you need to do ... */

let methodFinish = Date()
let executionTime = methodFinish.timeIntervalSince(methodStart)
print("Execution time: \(executionTime)")

易于使用，具有亚毫秒精度。