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An extension to Alamofire which automatically converts JSON response data into swift objects using ObjectMapper.
Given a URL which returns weather data in the following form:
{
"location": "Toronto, Canada",
"three_day_forecast": [
{
"conditions": "Partly cloudy",
"day" : "Monday",
"temperature": 20
},
{
"conditions": "Showers",
"day" : "Tuesday",
"temperature": 22
},
{
"conditions": "Sunny",
"day" : "Wednesday",
"temperature": 28
}
]
}
You can use the extension as the follows:
import AlamofireObjectMapper
let URL = "https://raw.githubusercontent.com/tristanhimmelman/AlamofireObjectMapper/d8bb95982be8a11a2308e779bb9a9707ebe42ede/sample_json"
Alamofire.request(URL).responseObject { (response: DataResponse<WeatherResponse>) in
let weatherResponse = response.result.value
print(weatherResponse?.location)
if let threeDayForecast = weatherResponse?.threeDayForecast {
for forecast in threeDayForecast {
print(forecast.day)
print(forecast.temperature)
}
}
}The WeatherResponse object in the completion handler is a custom object which you define. The only requirement is that the object must conform to ObjectMapper's Mappable protocol. In the above example, the WeatherResponse object looks like the following:
import ObjectMapper
class WeatherResponse: Mappable {
var location: String?
var threeDayForecast: [Forecast]?
required init?(map: Map){
}
func mapping(map: Map) {
location <- map["location"]
threeDayForecast <- map["three_day_forecast"]
}
}
class Forecast: Mappable {
var day: String?
var temperature: Int?
var conditions: String?
required init?(map: Map){
}
func mapping(map: Map) {
day <- map["day"]
temperature <- map["temperature"]
conditions <- map["conditions"]
}
}The extension uses Generics to allow you to create your own custom response objects. Below is the responseObject function definition. Just replace T in the completionHandler with your custom response object and the extension handles the rest:
public func responseObject<T: BaseMappable>(queue: DispatchQueue? = nil, keyPath: String? = nil, mapToObject object: T? = nil, context: MapContext? = nil, completionHandler: @escaping (DataResponse<T>) -> Void) -> SelfThe responseObject function has 4 optional parameters and a required completionHandler:
- queue: The queue on which the completion handler is dispatched.
- keyPath: The key path of the JSON where object mapping should be performed.
- mapToObject: An object to perform the mapping on to.
- context: A context object that is passed to the mapping function.
- completionHandler: A closure to be executed once the request has finished and the data has been mapped by ObjectMapper.
AlamofireObjectMapper supports dot notation within keys for easy mapping of nested objects. Given the following JSON String:
"distance" : {
"text" : "102 ft",
"value" : 31
}You can access the nested objects as follows:
func mapping(map: Map) {
distance <- map["distance.value"]
}The keyPath variable is used to drill down into a JSON response and only map the data found at that keyPath. It supports nested values such as data.weather to drill down several levels in a JSON response.
let URL = "https://raw.githubusercontent.com/tristanhimmelman/AlamofireObjectMapper/2ee8f34d21e8febfdefb2b3a403f18a43818d70a/sample_keypath_json"
let expectation = expectationWithDescription("\(URL)")
Alamofire.request(URL).responseObject(keyPath: "data") { (response: DataResponse<WeatherResponse>) in
expectation.fulfill()
let weatherResponse = response.result.value
print(weatherResponse?.location)
if let threeDayForecast = weatherResponse?.threeDayForecast {
for forecast in threeDayForecast {
print(forecast.day)
print(forecast.temperature)
}
}
}If you have an endpoint that returns data in Array form you can map it with the following function:
public func responseArray<T: Mappable>(queue queue: dispatch_queue_t? = nil, keyPath: String? = nil, completionHandler: DataResponse<[T]> -> Void) -> SelfFor example, if your endpoint returns the following:
[
{
"conditions": "Partly cloudy",
"day" : "Monday",
"temperature": 20
},
{
"conditions": "Showers",
"day" : "Tuesday",
"temperature": 22
},
{
"conditions": "Sunny",
"day" : "Wednesday",
"temperature": 28
}
]
You can request and map it as follows:
let URL = "https://raw.githubusercontent.com/tristanhimmelman/AlamofireObjectMapper/f583be1121dbc5e9b0381b3017718a70c31054f7/sample_array_json"
Alamofire.request(URL).responseArray { (response: DataResponse<[Forecast]>) in
let forecastArray = response.result.value
if let forecastArray = forecastArray {
for forecast in forecastArray {
print(forecast.day)
print(forecast.temperature)
}
}
}AlamofireObjectMapper can be added to your project using CocoaPods by adding the following line to your Podfile:
pod 'AlamofireObjectMapper', '~> 5.2'
If you're using Carthage you can add a dependency on AlamofireObjectMapper by adding it to your Cartfile:
github "tristanhimmelman/AlamofireObjectMapper" ~> 5.2