pod 'SnapKit'

然后 导入

//
//  ViewController.swift
//  videowallpaper
//
//  Created by liuan on 2020/6/11.
//  Copyright © 2020 liuan. All rights reserved.
//

import UIKit
import SnapKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        view.backgroundColor = .white
        test1()

    }
    
    func test1(){
        let box = UIView()
        view.addSubview(box)
        
        box.backgroundColor = .green
        //自动布局  添加约束 宽高==50  center = 父布局的center
        box.snp.makeConstraints{(make)->Void in
            make.width.height.equalTo(50)
            make.center.equalTo(self.view)
        }
    }
}

也可以用来设置边距

//
//  ViewController.swift
//  videowallpaper
//
//  Created by liuan on 2020/6/11.
//  Copyright © 2020 liuan. All rights reserved.
//

import UIKit
import SnapKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        view.backgroundColor = .white
        test1()

    }
    
    func test1(){
        let box = UIView()
        view.addSubview(box)
        
        box.backgroundColor = .green
        //自动布局  添加约束 宽高==50  center = 父布局的center
        box.snp.makeConstraints{(make)->Void in
            make.top.equalTo(view).offset(20)
              make.left.equalTo(view).offset(20)
              make.bottom.equalTo(view).offset(-20)
              make.right.equalTo(view).offset(-20)
        }
    }
}

就等价与下面这行代码

//
//  ViewController.swift
//  videowallpaper
//
//  Created by liuan on 2020/6/11.
//  Copyright © 2020 liuan. All rights reserved.
//

import UIKit
import SnapKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        view.backgroundColor = .white
        test1()

    }
    
    func test1(){
        let box = UIView()
        view.addSubview(box)
        
        box.backgroundColor = .green
        //自动布局  添加约束 宽高==50  center = 父布局的center
        box.snp.makeConstraints{(make)->Void in
            make.edges.equalTo(view).inset(UIEdgeInsets(top: 20, left: 20, bottom: 20, right: 20))
           
        }
    }
}