ios - 使用NSLayoutConstraint时引起的编译错误

Question

当我使用NSLayoutConstraint时，我的代码无法编译。我正在尝试使用代码做所有事情，而不使用 Storyboard 。我不知道这种情况是否正在发生，因为我缺少了一些东西，但它没什么意义，我现在就可以想到为什么它不起作用。该错误发生在judo = line的viewDidLoad函数中。

我收到错误消息:

Cannot assign value of type '[()]' to type '[NSLayout

用于 judo = []部分。

import UIKit

class ViewController: UIViewController {
    var Judo1 = [NSLayoutConstraint]()
    let FIRE = UIImageView()

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(FIRE)
        FIRE.translatesAutoresizingMaskIntoConstraints = false
        let leadingc2 = FIRE.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
        let trailingC2 =  FIRE.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0).isActive = true
        let topc2 =
            FIRE.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0).isActive = true
        let bottomc2 =   FIRE.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0).isActive = true

        Judo1 = [leadingc2,trailingC2,topc2,bottomc2]

        NSLayoutConstraint.activate(Judo1)
    }
}

Answer 1

当您追加

 .active = true

没有约束返回，因此使它们没有 .active = true，因为在这种情况下返回为空

FIRE.translatesAutoresizingMaskIntoConstraints = false
let leadingc2 = FIRE.topAnchor.constraint(equalTo: view.topAnchor, constant: 0)
let trailingC2 =  FIRE.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0)
let topc2 =   FIRE.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0)
let bottomc2 = FIRE.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0)  
judo1 = [leadingc2,trailingC2,topc2,bottomc2] 
NSLayoutConstraint.activate(judo1)

使用苹果推荐的更好方法(如果您不需要引用)

NSLayoutConstraint.activate ([

   FIRE.topAnchor.constraint(equalTo: view.topAnchor),
   FIRE.bottomAnchor.constraint(equalTo: view.bottomAnchor),
   FIRE.leadingAnchor.constraint(equalTo: view.leadingAnchor),
   FIRE.trailingAnchor.constraint(equalTo: view.trailingAnchor)

 ])

同样当常数为零时，摆脱它