如何根据不同的id绘制google地图标记，Swift

Question

在我当前的项目中，我收到了 api 的回复，如下所示：

[
{
  "current_location" : [
    90.458456400000003,
    23.746056500000002
  ],
  "vehicle_type" : "BIKE",
  "_id" : "5a8fd7e50ed19875687dcf8c"
},
{
  "current_location" : [
    90.3727272,
    23.8216228
  ],
  "vehicle_type" : "BIKE",
  "_id" : "5a97f48edf192f6e54725c78"
},
{
  "current_location" : [
    90.397113300000001,
    23.778111200000001
  ],
  "vehicle_type" : "BIKE",
  "_id" : "5a980243df192f6e54725c85"
},
{
  "current_location" : [
    90.379659399999994,
    23.7221121
  ],
  "vehicle_type" : "BIKE",
  "_id" : "5a9a66586f27706a7a10783a"
},
{
  "current_location" : [
    90.400972899999999,
    23.872647400000002
  ],
  "vehicle_type" : "BIKE",
  "_id" : "5a9fff2e31eb895bc79f7ee0"
 }
]

现在我制作了一个模型 class，随后在必要时在不同的 ViewController 中声明了该模型类型的数组。

var nearByFetchedVehicles = [nearByVehicleModel]()

现在，正如您在响应中看到的，我们得到了车辆的 _id。当我遍历 nearByFetchedVehicles 数组时，我想为每个 _id[=31= 创建 google 地图标记（当然会使用一些车辆图像） ].当我们在五秒后再次调用该函数时，我想检查 _id 是否存在，如果存在则我将检查纬度和经度并相应地移动标记，我有运动功能已经涵盖。该函数将每五秒调用一次，因此它需要不断检查哪个 _id 已经消失，哪个 _id 是新的。如果任何 _id 消失，之前存在的标记将被删除，如果新的 _id 可用，则将创建新标记。关于 _id，我需要帮助来创建标记并删除它。

if let fetchedVehicle = result.value { if fetchedVehicle.isEmpty { print("No vehicle nearby") } self.nearByFetchedVehicles = fetchedVehicle print("nearByFetchedVehicles are:\(self.nearByFetchedVehicles)") self.mapView?.clear() for i in self.nearByFetchedVehicles { // Need to create or delete marker here self.nearbyVehicleMovement(lat: i.lat!, lon: i.lon!, vehicleType: i.vehicleType!, vehicleID: i.vehicleID!) } }

Answer 1

我建议使用 Set 而不是 Array。它有 go substracting 方法，可以轻松处理您的数据。

//: Playground - noun: a place where people can play

import UIKit

var previousStr = """
[
{
"current_location" : [
90.458456400000003,
23.746056500000002
],
"vehicle_type" : "BIKE",
"_id" : "5a8fd7e50ed19875687dcf8c"
},
{
"current_location" : [
90.3727272,
23.8216228
],
"vehicle_type" : "BIKE",
"_id" : "5a97f48edf192f6e54725c78"
},
{
"current_location" : [
90.397113300000001,
23.778111200000001
],
"vehicle_type" : "BIKE",
"_id" : "5a980243df192f6e54725c85"
},
{
"current_location" : [
90.379659399999994,
23.7221121
],
"vehicle_type" : "BIKE",
"_id" : "5a9a66586f27706a7a10783a"
},
{
"current_location" : [
90.400972899999999,
23.872647400000002
],
"vehicle_type" : "BIKE",
"_id" : "5a9fff2e31eb895bc79f7ee0"
}
]
"""

var str = """
[
{
"current_location" : [
90.458456400000003,
23.746056500000002
],
"vehicle_type" : "BIKE",
"_id" : "5a8fd7e50ed19875687dcf8c"
},
{
"current_location" : [
90.3727272,
23.8216228
],
"vehicle_type" : "BIKE",
"_id" : "5a97f48edf192f6e54725c78"
},
{
"current_location" : [
90.397113300000001,
23.778111200000001
],
"vehicle_type" : "BIKE",
"_id" : "5a980243df192f6e54725c85"
},
{
"current_location" : [
90.379659399999994,
23.7221121
],
"vehicle_type" : "BIKE",
"_id" : "5a9a66586f27706a7a10783a"
},
{
"current_location" : [
90.400972899999999,
23.872647400000002
],
"vehicle_type" : "BIKE",
"_id" : "5a9fff2e31eb895bc79f7ee0"
}
]
"""

struct Vehicle: Decodable, Hashable {
    let current_location: [Double]
    let vehicle_type: String
    let _id: String

    var hashValue: Int {
        return _id.hashValue
    }
}
let array: [Vehicle] = try! JSONDecoder().decode([Vehicle].self, from: str.data(using: .utf8)!)
let set = Set<Vehicle>(array)

let previousArray: [Vehicle] = try! JSONDecoder().decode([Vehicle].self, from: previousStr.data(using: .utf8)!)
let previousSet = Set<Vehicle>(previousArray)

print(previousSet)

let added = set.subtracting(previousSet)
let lost = previousSet.subtracting(set)

print(added)
print(lost)

产生这个：

[__lldb_expr_63.Vehicle(current_location: [90.3727272, 23.8216228], vehicle_type: "BIKE", _id: "5a97f48edf192f6e54725c78"), __lldb_expr_63.Vehicle(current_location: [90.397113300000001, 23.778111200000001], vehicle_type: "BIKE", _id: "5a980243df192f6e54725c85"), __lldb_expr_63.Vehicle(current_location: [90.379659399999994, 23.7221121], vehicle_type: "BIKE", _id: "5a9a66586f27706a7a10783a"), __lldb_expr_63.Vehicle(current_location: [90.400972899999999, 23.872647400000002], vehicle_type: "BIKE", _id: "5a9fff2e31eb895bc79f7ee0"), __lldb_expr_63.Vehicle(current_location: [90.458456400000003, 23.746056500000002], vehicle_type: "BIKE", _id: "5a8fd7e50ed19875687dcf8c")] added>>>>> [__lldb_expr_63.Vehicle(current_location: [90.400972899999999, 23.872647400000002], vehicle_type: "BIKE", _id: "5a9fff2e31eb895bc79f7ee1")] lost>>>> [__lldb_expr_63.Vehicle(current_location: [90.400972899999999, 23.872647400000002], vehicle_type: "BIKE", _id: "5a9fff2e31eb895bc79f7ee0")]

在您的情况下，您可以使用 let previousSet = set.

轻松存储以前的数据

Answer 2

两种方式：

每次从服务器获得响应时，使用 mapView.clear() 清除 mapView。然后再次绘制标记。
将_id作为用户数据分配给每个maker，如marker.userData = _id。将标记存储在一个数组中，并通过 markerArray 循环。检查标记 _id 是否存在于来自服务器的数组中。如果不存在，请删除标记，如 marker.map = nil。否则使用
更改标记位置
```
marker.position = CLLocationCoordinate2D.init(latitude: <#T##CLLocationDegrees#>, longitude: <#T##CLLocationDegrees#>)
```

如果标记中的 _id 与任何 标记的 userData 都不匹配，则创建一个新标记为：

let marker = GMSMarker.init(position: currentLocation)
marker.map = mapView
marker.userData = nearByFetchedVehicles[i]

希望对您有所帮助。

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