无法将“[String]”类型的值分配给“String”类型？斯威夫特 2答案

【问题标题】：Cannot assign value of type '[String]' to type 'String? Swift 2无法将“[String]”类型的值分配给“String”类型？斯威夫特 2
【发布时间】：2016-07-08 08:50:14
【问题描述】：

我收到与此行“point.title = r”和此行“point.subtitle = z”相关联的错误消息“无法将类型'[String]' 的值分配给类型'String？'”。我已经尝试了很多类似 place.description 的方法，它使整个数组成为一个字符串...

//I have multiple arrays, lat, long and pass besides place.
var place = [String]()

//I have four of the chunks of code for each array
let json = try NSJSONSerialization.JSONObjectWithData(jSONData, options: .AllowFragments)
            if let dataFile3 = json["data"] as? [[String: AnyObject]] {
                for c in dataFile3 {
                    if let placeName = c["PlaceName"] {
                        place.append((placeName as? String)!)

for var (i,x) in zip(lat, long) {
            for _ in place {
                for _ in pass {
            print(i)
            print(x)
            //print(i + ", " + x)

        // String to double conversion, can I do this when I set the array as a string?
        let lati = NSString(string: i).doubleValue
        let longi = NSString(string: x).doubleValue


        //I have a list of values array so I need to have a for loop that inputs the value over and over again.
        var point = MGLPointAnnotation()
            point.coordinate = CLLocationCoordinate2D(latitude: lati, longitude: longi)

            point.title = place
            point.subtitle = pass

        mapView.addAnnotation(point)
            }}}

        //var i and x for loop
        }

    //viewDidLoad
    }

    //creates the markers popup for each point with data
    func mapView(mapView: MGLMapView, annotationCanShowCallout annotation: MGLAnnotation) -> Bool {
        // Always try to show a callout when an annotation is tapped.
        return true
    }

如何解决上述错误？

编辑：在 Santosh 的帮助下，我改变了这一切……

let point = MGLPointAnnotation()

        var i = lat
        var x = long

        //lat and long is served and then all the r,z points, then another lat, long...need to fix this and it may work.
        for (i,x) in zip(lat, long) {
            for aPlace in place {
                for aPass in pass {
            print(i)
            print(x)

        // String to double conversion, can I do this when I set the array as a string?
        let lati = NSString(string: i).doubleValue
        let longi = NSString(string: x).doubleValue

        point.coordinate = CLLocationCoordinate2D(latitude: lati, longitude: longi)


            point.title = aPlace
            print(aPlace)


            point.subtitle = aPass
            print(aPass)

        self.mapView.addAnnotation(point)
            }}}

现在运行正常，或者至少报告了正确的值，但循环只是保持循环......

【问题讨论】：

place 是一个array，因此您需要从该数组中访问该项目。因为point.title 接受optional String，即String?。这就是错误所说的。
是的，这基本上就是我的想法，只是不知道如何解决它......我在下面使用你的建议，但不幸的是我认为它没有任何区别。我非常感谢您的努力。
你在下面的答案中遇到了什么错误？
在上面添加了一个新块供您查看。需要在 105 条记录后停止循环。
我看到了 3 个循环，因此请检查哪个循环具有更多值并将其限制为您想要的任何值。

标签： ios swift2 mapbox

【解决方案1】：

试试这个：

//I have four of the chunks of code for each array
    let json = try NSJSONSerialization.JSONObjectWithData(jSONData, options: .AllowFragments)
    if let dataFile3 = json["data"] as? [[String: AnyObject]] {
        for c in dataFile3 {
            if let placeName = c["PlaceName"] {
                place.append((placeName as? String)!)

                for var (i,x) in zip(lat, long) {
                    for aPlace in place {
                        for aPass in pass {
                            print(i)
                            print(x)
                            //print(i + ", " + x)

                            // String to double conversion, can I do this when I set the array as a string?
                            let lati = NSString(string: i).doubleValue
                            let longi = NSString(string: x).doubleValue


                            //I have a list of values array so I need to have a for loop that inputs the value over and over again.
                            var point = MGLPointAnnotation()
                            point.coordinate = CLLocationCoordinate2D(latitude: lati, longitude: longi)

                            point.title = aPlace
                            point.subtitle = aPass

                            mapView.addAnnotation(point)
                        }}}

                //var i and x for loop
            }

            //viewDidLoad
        }
}

【讨论】：