函数返回值

Question

我有一个函数，它是WebScraping代码的一部分。在函数中，我有一个想要在图表中显示的值。要做到这一点，我需要从函数parseElevation()中获取变量“海拔”。我试过了

func parseElevation() -> String {

但是，这不起作用，因为变量“海拔”是“一层更深”。

这是代码：

func parseElevation()  {
        webView.evaluateJavaScript("document.body.innerHTML") { result, error in
            guard let html = result as? String, error == nil else {
                return
            }
            
            let leftSideOfTheValue = """
            <pre style="word-wrap: break-word; white-space: pre-wrap;">
            """
            
            let rightSideOfTheValue = """
            </pre>
            """
            
            guard let leftRange = html.range(of: leftSideOfTheValue) else {
                print("cant find left range")
                return
            }
            
            guard let righRange = html.range(of: rightSideOfTheValue) else {
                print("cant find right range")
                return
            }
            
            let rangeOfTheValue = leftRange.upperBound..<righRange.lowerBound
            
            let elevationInfo = (html[rangeOfTheValue])
            
            let last9 = elevationInfo.suffix(11)
            
            if let index = (last9.range(of: ",")?.upperBound)
            {
              //prints "value"
              let afterEqualsTo = String(last9.suffix(from: index))
                print(afterEqualsTo)
                let elevation = afterEqualsTo
                
            }
        }
        
    }

有人知道如何解决这个问题吗。我一直以来都有一个问题，返回价值观的迅速。

Answer 1

不能从没有返回值的闭包中返回某些内容。

您需要异步完成处理程序。

func parseElevation(completion: @escaping (String) -> Void)  {
    webView.evaluateJavaScript("document.body.innerHTML") { result, error in
        guard let html = result as? String, error == nil else {
            return
        }
        
        let leftSideOfTheValue = """
        <pre style="word-wrap: break-word; white-space: pre-wrap;">
        """
        
        let rightSideOfTheValue = """
        </pre>
        """
        
        guard let leftRange = html.range(of: leftSideOfTheValue) else {
            print("cant find left range")
            return
        }
        
        guard let righRange = html.range(of: rightSideOfTheValue) else {
            print("cant find right range")
            return
        }
        
        let rangeOfTheValue = leftRange.upperBound..<righRange.lowerBound
        
        let elevationInfo = (html[rangeOfTheValue])
        
        let last9 = elevationInfo.suffix(11)
        
        if let index = (last9.range(of: ",")?.upperBound)
        {
            //prints "value"
            let afterEqualsTo = String(last9.suffix(from: index))
            completion(afterEqualsTo)                
        }
    } 
}

然后叫它

parseElevation { elevation in
    print(elevation)
}

备注：

第二个片段中的

• elevation仅在闭包{}.

中可用。

• 认为，只有在计算结果时才调用完成处理程序。所有return语句都安静地离开闭包.