是否有一种方法可以确定一个方法需要执行多少时间(以毫秒为单位)?
当前回答
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。
其他回答
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;
你可以得到很好的时间(秒。部分秒)使用这个StopWatch类。它使用了iPhone的高精度计时器。使用NSDate只能获得秒级精度。这个版本是专门为自动发布和objective-c设计的。如果需要的话,我也有一个c++版本。你可以在这里找到c++版本。
StopWatch.h
#import <Foundation/Foundation.h>
@interface StopWatch : NSObject
{
uint64_t _start;
uint64_t _stop;
uint64_t _elapsed;
}
-(void) Start;
-(void) Stop;
-(void) StopWithContext:(NSString*) context;
-(double) seconds;
-(NSString*) description;
+(StopWatch*) stopWatch;
-(StopWatch*) init;
@end
StopWatch.m
#import "StopWatch.h"
#include <mach/mach_time.h>
@implementation StopWatch
-(void) Start
{
_stop = 0;
_elapsed = 0;
_start = mach_absolute_time();
}
-(void) Stop
{
_stop = mach_absolute_time();
if(_stop > _start)
{
_elapsed = _stop - _start;
}
else
{
_elapsed = 0;
}
_start = mach_absolute_time();
}
-(void) StopWithContext:(NSString*) context
{
_stop = mach_absolute_time();
if(_stop > _start)
{
_elapsed = _stop - _start;
}
else
{
_elapsed = 0;
}
NSLog([NSString stringWithFormat:@"[%@] Stopped at %f",context,[self seconds]]);
_start = mach_absolute_time();
}
-(double) seconds
{
if(_elapsed > 0)
{
uint64_t elapsedTimeNano = 0;
mach_timebase_info_data_t timeBaseInfo;
mach_timebase_info(&timeBaseInfo);
elapsedTimeNano = _elapsed * timeBaseInfo.numer / timeBaseInfo.denom;
double elapsedSeconds = elapsedTimeNano * 1.0E-9;
return elapsedSeconds;
}
return 0.0;
}
-(NSString*) description
{
return [NSString stringWithFormat:@"%f secs.",[self seconds]];
}
+(StopWatch*) stopWatch
{
StopWatch* obj = [[[StopWatch alloc] init] autorelease];
return obj;
}
-(StopWatch*) init
{
[super init];
return self;
}
@end
该类有一个返回自动释放对象的静态stopWatch方法。
调用start后,使用seconds方法获取运行时间。再次调用start来重新启动它。或者停下来停下来。在调用stop后,您仍然可以随时读取时间(调用秒数)。
函数中的示例(执行的定时调用)
-(void)SomeFunc
{
StopWatch* stopWatch = [StopWatch stopWatch];
[stopWatch Start];
... do stuff
[stopWatch StopWithContext:[NSString stringWithFormat:@"Created %d Records",[records count]]];
}
struct TIME {
static var ti = mach_timebase_info()
static var k: Double = 1
static var mach_stamp: Double {
if ti.denom == 0 {
mach_timebase_info(&ti)
k = Double(ti.numer) / Double(ti.denom) * 1e-6
}
return Double(mach_absolute_time()) * k
}
static var stamp: Double { return NSDate.timeIntervalSinceReferenceDate() * 1000 }
}
do {
let mach_start = TIME.mach_stamp
usleep(200000)
let mach_diff = TIME.mach_stamp - mach_start
let start = TIME.stamp
usleep(200000)
let diff = TIME.stamp - start
print(mach_diff, diff)
}
对于Swift 4,添加一个委托到你的类:
public protocol TimingDelegate: class {
var _TICK: Date?{ get set }
}
extension TimingDelegate {
var TICK: Date {
_TICK = Date()
return(_TICK)!
}
func TOCK(message: String) {
if (_TICK == nil){
print("Call 'TICK' first!")
}
if (message == ""){
print("\(Date().timeIntervalSince(_TICK!))")
}
else{
print("\(message): \(Date().timeIntervalSince(_TICK!))")
}
}
}
加入我们班:
class MyViewcontroller: UIViewController, TimingDelegate
然后添加到你的类:
var _TICK: Date?
当你想为某事计时时,可以从以下开始:
TICK
最后:
TOCK("Timing the XXX routine")
我使用基于Ron的解决方案的宏。
#define TICK(XXX) NSDate *XXX = [NSDate date]
#define TOCK(XXX) NSLog(@"%s: %f", #XXX, -[XXX timeIntervalSinceNow])
对于代码行:
TICK(TIME1);
/// do job here
TOCK(TIME1);
我们将在控制台中看到如下内容:TIME1: 0.096618
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