objective-c - 初始化之前使用的变量注释

Question

您好，下面是 CCHMapClusterController 的代码。我尝试将此函数重写为 Swift，但我不断收到此错误:

“初始化之前使用的变量注释”

上线: clusterAnnotation = 注释

我对 Objective C 一无所知，有人可以检查我是否正确执行了最后几行吗？

objective-c :

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:    (id<MKAnnotation>)annotation
{
    MKAnnotationView *annotationView;

    if ([annotation isKindOfClass:CCHMapClusterAnnotation.class]) {
    static NSString *identifier = @"clusterAnnotation";

    ClusterAnnotationView *clusterAnnotationView = (ClusterAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:identifier];
    if (clusterAnnotationView) {
        clusterAnnotationView.annotation = annotation;
    } else {
        clusterAnnotationView = [[ClusterAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier];
        clusterAnnotationView.canShowCallout = YES;
    }

    CCHMapClusterAnnotation *clusterAnnotation = (CCHMapClusterAnnotation *)annotation;
    clusterAnnotationView.count = clusterAnnotation.annotations.count;
    clusterAnnotationView.blue = (clusterAnnotation.mapClusterController == self.mapClusterControllerBlue);
    clusterAnnotationView.uniqueLocation = clusterAnnotation.isUniqueLocation;
    annotationView = clusterAnnotationView;
}

return annotationView;
}

Swift 代码:

func mapView(mapView: MKMapView!, viewForAnnotation annotation: MKAnnotation!) -> MKAnnotationView! {
    if annotation is MKUserLocation {
        // return nil so map view draws "blue dot" for standard user location
        return nil
    }

    var annotationView : MKAnnotationView?


    if annotation is CCHMapClusterAnnotation {
      //  let a : clusterAnnotationView = annotation as clusterAnnotationView

        let identifier: NSString = "clusterAnnotation"
        var clusterAnnotationView = (mapView.dequeueReusableAnnotationViewWithIdentifier(identifier as String)) as? ClusterAnnotationView!

        if (clusterAnnotationView != nil) {
            clusterAnnotationView!.annotation = annotation
        } else {
            clusterAnnotationView = ClusterAnnotationView(annotation: annotation, reuseIdentifier: "clusterAnnotation")
            clusterAnnotationView!.canShowCallout = true
        }

        var clusterAnnotation : CCHMapClusterAnnotation;
        var annotation : CCHMapClusterAnnotation
        clusterAnnotation = annotation
        clusterAnnotationView.count = clusterAnnotation.annotations.count
        clusterAnnotationView!.blue = (clusterAnnotation.mapClusterController == self.mapClusterControllerBlue);
        clusterAnnotationView!.uniqueLocation = clusterAnnotation.isUniqueLocation();
        annotationView = clusterAnnotationView

    }

Answer 1

用这些行:

var clusterAnnotation : CCHMapClusterAnnotation;
var annotation : CCHMapClusterAnnotation
clusterAnnotation = annotation

声明了两个变量但未初始化，因此您会收到该警告。

此外，它还声明了一个与现有 annotation 参数同名的新局部变量 annotation。您也可能会收到警告或错误。

如果您尝试转换此 Objective-C 行:

CCHMapClusterAnnotation *clusterAnnotation = 
    (CCHMapClusterAnnotation *)annotation;

将 annotation 参数转换为 CCHMapClusterAnnotation，那么可能的 Swift 版本是:

let clusterAnnotation = annotation as? CCHMapClusterAnnotation

但是，您也可以将上面的注释类检查(if comment is ...)与此强制转换赋值结合起来:

if let clusterAnnotation = annotation as? CCHMapClusterAnnotation {
    ...
}