我使用 CoreLocation 计算了距离，但无法将距离分配给变量并在 Tableview 中显示该值。
我使用 forwardGeocoding 函数将 String 转换为 CLLocation 类型并获得两个点之间的距离。我可以打印闭包内的数据，但我永远无法将距离分配给闭包外的变量。
// This function will accept a string and convert to CLLocation
func forwardGeocoding(address:String, completion: @escaping ((CLLocation?) -> Void))
{
let geocoder = CLGeocoder()
geocoder.geocodeAddressString(address, completionHandler: { (placemarks, error) in
if let error = error
{
print(error)
completion(nil)
}
else
{
// found locations, then perform the next task using closure
let placemark = placemarks?[0]
completion(placemark?.location) // execute closure
}
})
}
// This function will find the distance, assign it to a local variable and return it
func searchDistance(_ address: String) -> Double
{
var distance: Double = 0
self.forwardGeocoding(address:address, completion: {(location) in
if let locationTo = location {
// calculate distance
distance = (self.mainDelegate.currLocation?.distance(from: locationTo))!
// distance has value here
print("distance in closure \(distance)")
} else {
// not found destination, show alert
print("cannot find address")
}
})
print(distance) // fails to catch the distance, always 0
return distance
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let tableCell = tableView.dequeueReusableCell(withIdentifier: "DonorCell", for: indexPath) as? DonorListTableViewCell ?? DonorListTableViewCell(style: .default, reuseIdentifier: "DonorCell")
let index = indexPath.row
tableCell.donorName?.text = donors[index].organizationName
tableCell.donorAddress?.text = "\(donors[index].street ?? ""), \( donors[index].city ?? "")"
tableCell.donorPhone?.text = donors[index].phoneNumber
let donorAddress = "\(donors[index].street ?? "") \(donors[index].city ?? "") \(donors[index].postalCode ?? "")"
// This is always 0
let distanceOnMap = searchDistance(donorAddress)
return tableCell
}
我认为这是@escaping 问题，但我不知道如何修改它以成功显示表格单元格中的距离。请帮忙
问题在我老师的帮助下解决了。解决方法是创建一个实例变量，然后在闭包中直接调用self.tableview.reload。在 tableView cellForRowAT 中，只需从实例变量加载值。
func searchAddress(_ address: String)
{
self.forwardGeocoding(address:address, completion: {(location) in
if let locationTo = location {
// calculate distance
self.donorDistance.append((self.mainDelegate.currLocation?.distance(from: locationTo) ?? 0))
print(self.mainDelegate.currLocation?.distance(from: locationTo) ?? 0)
if self.donorDistance.count == self.donors.count
{
self.tableview.reloadData()
}
} else {
// not found destination, show alert
print("cannot find address")
}
})
}
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