CGPathMoveToPoint在創建路徑

Question

我使用以下代碼從CGPoint array（）創建路徑時遇到了一些問題。

public func creatPath (for points:[CGPoint]) { 
    let path = CGMutablePath() 
    let startPoint = points.first 

    CGPathMoveToPoint(path, CGAffineTransform.identity, startPoint.x, startPoint.y) 

    var index = 0 
    for point in points { 
     if index == 0 { continue } 
     CGPathAddLineToPoint(path, nil, points.x, points.y) 
     index += 1 
    } 
    path.closeSubpath() 
} 

但它最終總是向我展示以下錯誤：

nil is not compatible with expected argument type UnsafePointer <CGAffineTransForm>

我一直在使用CGAffineTransform.identity也嘗試過那麼就說明：

Cannot convert value of type 'CGAffineTransform' to expected argument type 'UnsafePointer <CGAffineTransform> '

我不知道我們可以用別的什麼這裏。我使用的測試Xcode8 6雨燕3.0

編輯：當我嘗試： -

var transform = CGAffineTransform.identity as CGAffineTransform; 
CGPathMoveToPoint(path, &transform, startPoint.x, startPoint.y) 

它顯示：

'CGPathMoveToPoint' is unavailable: Use move(to:transform:)

雖然嘗試：

CGPathMoveToPoint(path, NSNull(), startPoint.x, startPoint.y) 

Error is: Cannot convert value of type 'NSNull' to expected argument type 'UnsafePointer'

Answer 1

Swift 3爲CGMutablePath提供了一個大大改進的，面向對象的接口。最棒的是：轉換參數有一個默認值，可以省略。

public func creatPath (for points:[CGPoint]) { 
    let path = CGMutablePath() 
    let startPoint = points.first 

    path.move(to: startPoint) 

    var index = 0 
    for point in points { 
     if index == 0 { continue } 
     path.addLine(to: point) 
     index += 1 
    } 
    path.closeSubpath() 
} 

注：我已經改變了循環變量從points到point以避免與參數名稱衝突。

更新

您可以簡化代碼：

public func creatPath (for points:[CGPoint]) { 
    let path = CGMutablePath() 
    path.addLines(between: points) 
    path.closeSubpath() 
}