Question

我正在使用Xcode 8.2.1，我的上一个项目的编译时间非常慢。我花了一些时间研究为什么会这样，我开始跟踪项目的编译时间。所以主要问题似乎在这里：

49,609.4ms来编译moveIcons（）

现在这对我来说有点意外，因为moveIcons（）并不是一个非常广泛的方法：

func moveIcons(_ motion : SlideMotion) {
    var direction : CGFloat = 1
    if motion == .Out {
        direction = -1
    }
    for icon in 0...3 {
        let currentIcon = pauseIcons[icon]
        var moveAction = SKAction.sequence([SKAction.move(by: CGVector(dx: (-scene.size.width * direction * 0.26) - (scene.size.width * 0.18 * direction), dy: 0), duration: 0.2), SKAction.move(by: CGVector(dx: scene.size.width * direction * 0.18, dy: 0), duration: 0.1)])
        if icon == 3 {
            moveAction = SKAction.sequence([SKAction.move(by: CGVector(dx: -scene.size.width * direction, dy: 0), duration: 0.3), SKAction.move(by: CGVector(dx: scene.size.width * direction * 0.25, dy: 0), duration: 0.15)])
        }
        currentIcon.run(moveAction)
    }
}

* pauseIcons初始化如下:(它可能像4个对象一样）

var pauseIcons : [SKSpriteNode] = []

现在我想也许问题是因为类型推断正在减慢构建速度。因此，我这样做了：

func moveIcons(_ motion : SlideMotion) {
    var direction : CGFloat = 1
    if motion == .Out {
        direction = -1
    }
    for icon in 0...3 {
        let currentIcon : SKSpriteNode = pauseIcons[icon]
        var moveAction : SKAction = SKAction.sequence([SKAction.move(by: CGVector(dx: (-scene.size.width * direction * 0.26) - (scene.size.width * 0.18 * direction), dy: 0), duration: 0.2), SKAction.move(by: CGVector(dx: scene.size.width * direction * 0.18, dy: 0), duration: 0.1)])
        if icon == 3 {
            moveAction = SKAction.sequence([SKAction.move(by: CGVector(dx: -scene.size.width * direction, dy: 0), duration: 0.3), SKAction.move(by: CGVector(dx: scene.size.width * direction * 0.25, dy: 0), duration: 0.15)])
        }
        currentIcon.run(moveAction)
    }
}

然而，编译时间仍然是我项目中最高的：

有没有人知道为什么这个特定方法需要花费这么多时间来编译？

Answer 1

这个表达式和相关表达式非常复杂：

var moveAction = SKAction.sequence([SKAction.move(by: CGVector(dx: (-scene.size.width * direction * 0.26) - (scene.size.width * 0.18 * direction), dy: 0), duration: 0.2), SKAction.move(by: CGVector(dx: scene.size.width * direction * 0.18, dy: 0), duration: 0.1)])

用中间变量打破这些。问题不在于找出最终的类型。问题是找出*和-的所有可能性。是的，只有一个有效的可能性，但编译器必须检查每个可能的类型组合，以确保表达式不含糊。特别是，它必须做很多工作来决定0.26是CGFloat，Float还是Double。

更多内容如下：

for icon in 0...3 {
    let currentIcon : SKSpriteNode = pauseIcons[icon]

    let moveAction: SKAction

    if icon == 3 {
        let moveBy1 = CGVector(dx: -scene.size.width * direction, dy: 0)
        let moveBy2 = CGVector(dx: scene.size.width * direction * 0.25, dy: 0)
        moveAction = SKAction.sequence([
            SKAction.move(by: moveBy1), duration: 0.3),
            SKAction.move(by: moveBy2, duration: 0.15)])
    } else {
        let moveBy1 = CGVector(dx: (-scene.size.width * direction * 0.26) - (scene.size.width * 0.18 * direction), dy: 0)
        let moveBy2 = CGVector(dx: scene.size.width * direction * 0.18, dy: 0)
        moveAction = SKAction.sequence([SKAction.move(by: moveBy1, duration: 0.2),
                                        SKAction.move(by: moveBy2, duration: 0.1)])
    }
    currentIcon.run(moveAction)
}

在Xcode中以特定方法缩短编译时间

1 个答案: