iOS设计模式之懒加载

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic,strong) UILabel * titleLabel;
@property (nonatomic,strong) UITextField *textField;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    [self initUI];
}

- (void)initUI
{
    //只是加载到预想加载的view上。不在初始化方法里为其alloc/init。只是一个指针，不会占内存。
    
    [self.view addSubview:self.titleLabel];
    
    [self.view addSubview:self.textField];
}

#pragma mark 重写titleLabel的getter方法
- (UILabel *)titleLabel
{
    
    if (!_titleLabel) {
        
        self.titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 20, 100, 40)];
        self.titleLabel.textAlignment = NSTextAlignmentCenter;
        self.titleLabel.text = @"你瞅啥";
        self.titleLabel.textColor = [UIColor blackColor];
        [self.titleLabel sizeToFit];
    }
    
    return _titleLabel;
}
#pragma mark 重写的textField的getter方法
- (UITextField *)textField
{
    if (!_textField) {
        self.textField = [[UITextField alloc] initWithFrame:CGRectMake(10, 100, 100, 40)];
        self.textField.borderStyle = UITextBorderStyleRoundedRect;
        self.textField.clearButtonMode = UITextFieldViewModeWhileEditing;
        self.textField.placeholder = @"瞅你咋滴";
    }
    return _textField;
}
@end