viewcontroller切换时，方法调用的顺序

         viewcontroller切换时，方法调用的顺序         

其实写了这么久的代码，真没有注意过这个问题，到底是viewdidload先调用还是viewdiddisappear先调用呢。

现在写了一个小例子来测测：

有两个viewcontroller，分别为ViewController(后面简称A)和BViewController(后面简称B)

//ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController


@end

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//ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

-(void)viewDidAppear:(BOOL)animated
{
    NSLog(@"A- viewDidAppear");
}

-(void)viewWillAppear:(BOOL)animated
{
    NSLog(@"A- viewWillAppear");
}

-(void)viewWillDisappear:(BOOL)animated
{
    NSLog(@"A- viewWillDisappear");
}

-(void)viewDidDisappear:(BOOL)animated
{
    NSLog(@"A- viewDidDisappear");
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSLog(@"A- viewDidLoad");
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

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//BViewController.h

#import <UIKit/UIKit.h>

@interface BViewController : UIViewController

@end

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//BViewController.m

#import "BViewController.h"

@interface BViewController ()

@end

@implementation BViewController

-(void)viewDidAppear:(BOOL)animated
{
    NSLog(@"B- viewDidAppear");
}

-(void)viewWillAppear:(BOOL)animated
{
    NSLog(@"B- viewWillAppear");
}

-(void)viewWillDisappear:(BOOL)animated
{
    NSLog(@"B- viewWillDisappear");
}

-(void)viewDidDisappear:(BOOL)animated
{
    NSLog(@"B- viewDidDisappear");
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSLog(@"B- viewDidLoad");
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end

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启动app,首先出现A,运行结果如下： 
2015-04-06 15:11:34.761 viewchange[729:25610] A- viewDidLoad 
2015-04-06 15:11:34.762 viewchange[729:25610] A- viewWillAppear 
2015-04-06 15:11:34.769 viewchange[729:25610] A- viewDidAppear 
继续点击按钮A–>B,运行结果如下： 
2015-04-06 15:12:15.670 viewchange[729:25610] B- viewDidLoad 
2015-04-06 15:12:15.675 viewchange[729:25610] A- viewWillDisappear 
2015-04-06 15:12:15.676 viewchange[729:25610] B- viewWillAppear 
2015-04-06 15:12:16.182 viewchange[729:25610] B- viewDidAppear 
2015-04-06 15:12:16.182 viewchange[729:25610] A- viewDidDisappear

清楚的知道这些运行顺序，让我更清楚在什么时候该做什么更合适。