Swift异步逆地理编码获取地址无法返回至saveButton方法问题求助

问题根因 #

CLGeocoder.reverseGeocodeLocation 是异步方法，不会立刻执行完成，你当前写的同步返回String的getLocation()方法，在逆地理编码的闭包还没返回结果的时候就已经执行结束了，所以永远拿不到地址值。闭包内部的return addr只是结束闭包本身的执行，并不会把值返回到getLocation()的调用方。

解决方案 #

方案1：闭包回调实现（兼容iOS 11+） #

先改造getLocation方法，去掉同步返回，改为通过逃逸闭包回传地址结果：

func getLocation(completion: @escaping (String) -> Void) {
    // 获取坐标
    let result = lm.getLocationCoordinates()
    entryLat = result.0
    entryLong = result.1
    
    let location = CLLocation(latitude: entryLat, longitude: entryLong)
    location.placemark { placemark, error in
        guard let placemark = placemark, let address = placemark.postalAddressFormatted else {
            print("Error:", error ?? "nil")
            completion("Unknown")
            return
        }
        print("formatted address: \(address)")
        completion(address)
    }
}

再改造saveButton方法，将Core Data保存逻辑移到闭包内部，等拿到地址后再执行：

func saveButton() {
    getLocation { [weak self] address in
        guard let self = self else { return }
        self.addr = address
        print("addr = \(address)")
        
        // 保存条目到Core Data
        let newEntry = CurrTrans(context: self.viewContext)
        newEntry.id = UUID()                            
        newEntry.entryDT = self.entryDT
        newEntry.entryDsc = self.entryDsc
        newEntry.moneyD = self.moneyD
        newEntry.entryLat = self.entryLat
        newEntry.entryLong = self.entryLong
        newEntry.address = address
        
        do {
            try self.viewContext.save()
            print("newEntry.address = \(newEntry.address ?? "")")
        } catch {
            print(error.localizedDescription)
        }
    }
}

方案2：async/await实现（iOS 15+ 推荐） #

语法更简洁，避免回调嵌套：
首先给CLLocation扩展新增异步方法：

extension CLLocation {
    func getPlacemark() async throws -> CLPlacemark? {
        return try await CLGeocoder().reverseGeocodeLocation(self).first
    }
}

改造saveButton方法，用Task包裹异步逻辑：

func saveButton() {
    // 先获取坐标
    let result = lm.getLocationCoordinates()
    entryLat = result.0
    entryLong = result.1
    let location = CLLocation(latitude: entryLat, longitude: entryLong)
    
    Task {
        do {
            guard let placemark = try await location.getPlacemark(), 
                  let address = placemark.postalAddressFormatted else {
                self.addr = "Unknown"
                return
            }
            self.addr = address
            
            // 保存到Core Data
            let newEntry = CurrTrans(context: self.viewContext)
            newEntry.id = UUID()
            newEntry.entryDT = entryDT
            newEntry.entryDsc = entryDsc
            newEntry.moneyD = moneyD
            newEntry.entryLat = entryLat
            newEntry.entryLong = entryLong
            newEntry.address = address
            
            try viewContext.save()
            print("newEntry.address = \(newEntry.address ?? "")")
        } catch {
            print("逆地理编码错误: \(error.localizedDescription)")
        }
    }
}

注意事项 #

• 苹果对逆地理编码接口有调用频率限制，短时间内发起过多请求会返回错误，建议做好防抖或本地缓存逻辑。
• Core Data的保存操作必须在对应context的队列执行，如果你使用的是主队列context，上述写法无需额外调整。

内容的提问来源于stack exchange，提问作者Galen Smith