Swift 3.0调用结果未使用[重复]

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这个问题已经有了答案:

Xcode 8 / Swift 3: “Expression of type UIViewController? is unused” warning 7 answers
Xcode 8 / Swift 3:“UIViewController的表达式?”未使用的“警告7答案?

I am writing in swift 3.0

我用的是swift 3.0

i have this code which gives me the warning result of call is unused

我有这段代码，它告诉我调用的警告结果是没有用的。

        public override init(){
            super.init()
        }

        public init(annotations: [MKAnnotation]){
            super.init()
            addAnnotations(annotations:  annotations)

        }

        public func setAnnotations(annotations:[MKAnnotation]){
            tree = nil
            addAnnotations(annotations: annotations)
        }

        public func addAnnotations(annotations:[MKAnnotation]){
            if tree == nil {
                tree = AKQuadTree()
            }

            lock.lock()
            for annotation in annotations {
    // The warning occurs at this line
         tree!.insertAnnotation(annotation: annotation)
            }
            lock.unlock()
        }

i have tried using this method in another classes but it still gives me the error the code for insertAnnotation is above

我曾在其他类中尝试过使用这个方法，但它仍然给出了上面的insertAnnotation代码的错误

func insertAnnotation(annotation:MKAnnotation) -> Bool {
        return insertAnnotation(annotation: annotation, toNode:rootNode!)
    }

    func insertAnnotation(annotation:MKAnnotation, toNode node:AKQuadTreeNode) -> Bool {

        if !AKQuadTreeNode.AKBoundingBoxContainsCoordinate(box: node.boundingBox!, coordinate: annotation.coordinate) {
            return false
        }

        if node.count < nodeCapacity {
            node.annotations.append(annotation)
            node.count += 1
            return true
        }

        if node.isLeaf() {
            node.subdivide()
        }

        if insertAnnotation(annotation: annotation, toNode:node.northEast!) {
            return true
        }

        if insertAnnotation(annotation: annotation, toNode:node.northWest!) {
            return true
        }

        if insertAnnotation(annotation: annotation, toNode:node.southEast!) {
            return true
        }

        if insertAnnotation(annotation: annotation, toNode:node.southWest!) {
            return true
        }


        return false

    }

i have tried many methods but just doesn't work but in swift 2.2 it works fine any ideas why this is happening??

我尝试过很多方法，但都没有用，但是在swift 2.2中，它很好用，你知道为什么会这样吗?

1 个解决方案

#1

332

You are getting this issue because the function you are calling returns a value but you are ignoring the result.

您会遇到这个问题，因为正在调用的函数返回一个值，但您忽略了结果。

There are two ways to solve this issue:

有两种方法可以解决这个问题:

Ignore the result by adding _ = in front of the function call

在函数调用前添加_ =忽略结果。
Add @discardableResult to the declaration of the function to silence the compiler

将@discardableResult添加到函数的声明中，以使编译器静默。

#1

332