多控制器

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如果发现控制器的View还在，但是view上面的数据不显示，极大可能是因为：控制器为局部变量，提前销毁了，需要创建强引用

#import "HMViewController.h"#import "HMOneViewController.h"#import "HMTwoViewController.h"#import "HMThreeViewController.h"@interface HMViewController ()- (IBAction)vc1;- (IBAction)vc2;- (IBAction)vc3;@property (nonatomic, strong) HMTestViewController *test;@property (nonatomic, strong) HMOneViewController *one;@property (nonatomic, strong) HMTwoViewController *two;@property (nonatomic, strong) HMThreeViewController *three;@end@implementation HMViewController- (HMOneViewController *)one{    if (!_one) {        self.one = [[HMOneViewController alloc] init];        self.one.view.frame = CGRectMake(10, 70, 300, 300);    }    return _one;}- (HMTwoViewController *)two{    if (!_two) {        self.two = [[HMTwoViewController alloc] init];        self.two.view.frame = CGRectMake(10, 70, 300, 300);    }    return _two;}- (HMThreeViewController *)three{    if (!_three) {        self.three = [[HMThreeViewController alloc] init];        self.three.view.frame = CGRectMake(10, 70, 300, 300);    }    return _three;}- (void)viewDidLoad{    [super viewDidLoad];    //    HMTestViewController *test = [[HMTestViewController alloc] init];//    test.view.frame = CGRectMake(100, 100, 200, 300);//    test.view.backgroundColor = [UIColor redColor];//    [self.view addSubview:test.view];//    self.test = test;        // 如果发现：控制器的view还在，但是view上面的数据不显示，极大可能是因为：控制器被提前销毁了        // 1.一个控制器的view是可以随意调整尺寸和位置的    // 2.一个控制器的view是可以随意添加到其他view中    // 3.如果将一个控制器的view，添加到其他view中显示，那么要想办法保证控制器不被销毁    // 4.原则：只要view在，view所在的控制器必须得在，这样才能保证view内部的数据和业务逻辑正常}- (IBAction)vc1 {    [self.two.view removeFromSuperview];    [self.three.view removeFromSuperview];    [self.view addSubview:self.one.view];}- (IBAction)vc2 {    [self.one.view removeFromSuperview];    [self.three.view removeFromSuperview];    [self.view addSubview:self.two.view];}- (IBAction)vc3 {    // 强引用， remove view不会销毁    [self.two.view removeFromSuperview];    [self.one.view removeFromSuperview];    [self.view addSubview:self.three.view];}@end

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