AutoLayout自动适配

AutoLayout自动适配非常关键，因为很常用。
让我们来看看关于按钮的自动适配：

//这里不需要设置大小，反正，反正是自动适配
    modelButton = [[UIButton alloc] init];
    modelButton.center = self.view.center;
    
    modelButton.layer.cornerRadius = 8;
    
    modelButton.backgroundColor = [UIColor brownColor];
    
    [modelButton setTitle:@"模态" forState:UIControlStateNormal];
    [modelButton addTarget:self action:@selector(modelAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:modelButton];
    
    //小伙伴，这句话可不能少，取消button的自动适配
    modelButton.translatesAutoresizingMaskIntoConstraints = NO;
    
    NSString *hVFL = @"H:|-topSpace-[button]-bottomSpace-|";
    NSString *vVFL = @"V:|-leftSpace-[button]-rightSpace-|";
    
    NSDictionary *metrics = @{@"topSpace":@100,@"bottomSpace":@50,@"leftSpace":@80,@"rightSpace":@90};
    
    NSDictionary *views =@{@"button":modelButton};
    
    
    NSArray *hConstraint = [NSLayoutConstraint constraintsWithVisualFormat:hVFL
                                                                   options:NSLayoutFormatDirectionLeadingToTrailing
                                                                    metrics:metrics
                                                                      views:views];
    
    NSArray *vConstraint = [NSLayoutConstraint constraintsWithVisualFormat:vVFL
                                                                   options:NSLayoutFormatDirectionLeadingToTrailing
                                                                   metrics:metrics
                                                                     views:views];
    
    NSMutableArray *constraintArray = [[NSMutableArray alloc] init];
    
    //这样不行的原因是因为：addObject只能存储对象，而不能存储对象数组  所以要用addObjectsFromArray
//    [constraintArray addObject:hConstraint];
//    [constraintArray addObject:vConstraint];
    
    [constraintArray addObjectsFromArray:hConstraint];
    [constraintArray addObjectsFromArray:vConstraint];
    [self.view addConstraints:constraintArray];
    
//    [self.view addConstraints:hConstraint];
//    [self.view addConstraints:vConstraint];

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