舉例說明：建立一個grayView（寬150 高100 距上200 距左100）

方法一：原生API 

    UIView *grayView = [UIView new];
    grayView.backgroundColor = [UIColor lightGrayColor];
    // 禁止將 autoresizingmask 轉換為 constraints
    grayView.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:grayView];
    
    // 新增 width 約束
    NSLayoutConstraint *widthConstraint = [NSLayoutConstraint constraintWithItem:grayView attribute:(NSLayoutAttributeWidth) relatedBy:(NSLayoutRelationEqual) toItem:nil attribute:(NSLayoutAttributeNotAnAttribute) multiplier:0.0 constant:150];
    // 新增 height 約束
    NSLayoutConstraint *heightConstraint = [NSLayoutConstraint constraintWithItem:grayView attribute:(NSLayoutAttributeHeight) relatedBy:(NSLayoutRelationEqual) toItem:nil attribute:(NSLayoutAttributeNotAnAttribute) multiplier:0.0 constant:100];
    // 新增 left 約束
    NSLayoutConstraint *leftConstraint = [NSLayoutConstraint constraintWithItem:grayView attribute:(NSLayoutAttributeLeft) relatedBy:(NSLayoutRelationEqual) toItem:self.view attribute:(NSLayoutAttributeLeft) multiplier:1.0 constant:100];
    // 新增 top 約束
    NSLayoutConstraint *topConstraint = [NSLayoutConstraint constraintWithItem:grayView attribute:(NSLayoutAttributeTop) relatedBy:(NSLayoutRelationEqual) toItem:self.view attribute:(NSLayoutAttributeTop) multiplier:1.0 constant:200];
    
    
    [grayView addConstraint:widthConstraint];
    [grayView addConstraint:heightConstraint];
    [self.view addConstraint:leftConstraint];
    [self.view addConstraint:topConstraint];
 

方法二：VFL(Visual Format Language)

    UIView *grayView = [UIView new];
    grayView.backgroundColor = [UIColor lightGrayColor];
    grayView.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:grayView];

    // format引數
    NSString *Hvfl = @"H:|-left-[grayView(150)]";
    NSString *Vvfl = @"V:|-top-[grayView(100)]";

    // 設定 margin 數值
    NSDictionary *metrics = @{@"top":@200,@"left":@100};

    // 把要新增約束的view 轉成字典
    NSDictionary *views = NSDictionaryOfVariableBindings(grayView);// 這個方法會自動把傳入的引數椅子墊的形式返回，字典的key就是其本身的名字，如@{@"grayView":grayView}

    // 新增對齊方式
    NSLayoutFormatOptions ops = NSLayoutFormatAlignAllLeft | NSLayoutFormatAlignAllTop;// 左邊與頂部

    
    NSArray *Hconstraints = [NSLayoutConstraint constraintsWithVisualFormat:Hvfl options:ops metrics:metrics views:views];

    NSArray *Vconstraints = [NSLayoutConstraint constraintsWithVisualFormat:Vvfl options:ops metrics:metrics views:views];


    [self.view addConstraints:Hconstraints];
    [self.view addConstraints:Vconstraints];
 

執行如下：

本篇部落格只是針對基礎知識點的整理歸納與簡單應用 詳細程式碼解析請參考如下部落格：