平常一些简化重复的代码

import SnapKit
extension ConstraintMaker {
    func equalToPreTop(preView: UIView?, offset: CGFloat, topOffset: CGFloat? = nil) {
        if let preView = preView {
            self.top.equalTo(preView.snp.bottom).offset(offset)
        } else {
            if let topOffset = topOffset, topOffset != 0 {
              self.top.equalToSuperview().offset(topOffset)
            } else {
              self.top.equalToSuperview()
           }
        }
    }
    func equalToPreLeft(preView: UIView?, offset: CGFloat, leftOffset: CGFloat? = nil) {
        if let preView = preView {
            self.left.equalTo(preView.snp.right).offset(offset)
        } else {
           if let leftOffset = leftOffset, leftOffset != 0 {
              self.left.equalToSuperview().offset(leftOffset)
            } else {
              self.left.equalToSuperview()
           }
        }
    }
    
    func equalToMargins( _ margin: CGFloat) {
        self.left.equalTo(margin)
        self.right.equalTo(-margin)
    }
    
    func equalToBottomLess(show: Bool?, margin: CGFloat) {
        if show == true {
            self.bottom.lessThanOrEqualToSuperview().offset(-margin)
        }
    }
}

使用在一些for循环出来添加到view上的场景
A
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B
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C

// 上下排列的样式
var topView: UIView? = nil
for i in (0..<10) {
let item = UIView()
self.addSubView(item)
item.snp.makeConstraints { make in
   // 具体相邻的顶部的view的bottom距离为10，如果没有顶部的view，等于父view的顶部20的距离
   make.equalToPreTop(preView: topView, offset: 10, topOffset: 20)
  // 距离左右15的距离
   make.equalToMargins(margin: 15)
   make.height.equalTo(20)
 }
  topView = item
}

E-F-G

// 左右排列的样式
var leftView: UIView? = nil
for i in (0..<10) {
let item = UIView()
self.addSubView(item)
item.snp.makeConstraints { make in
   // 具体相邻的顶部的view的右侧距离为10，如果没有左部的view，等于父view的左部20的距离
   make.equalToPreLeft(leftView: leftView, offset: 10, leftOffset: 20)
   make.width(80)
   make.height.equalTo(20)
 }
  leftView = item
}