对于Alamofire的result：
<code>public enum Result<Value, Error : ErrorType> {
case Success(Value)
case Failure(Error)
/// Returns `true` if the result is a success, `false` otherwise.
public var isSuccess: Bool { get }
/// Returns `true` if the result is a failure, `false` otherwise.
public var isFailure: Bool { get }
/// Returns the associated value if the result is a success, `nil` otherwise.
public var value: Value? { get }
/// Returns the associated error value if the result is a failure, `nil` otherwise.
public var error: Error? { get }
}
</code>现在对于函数：
<code> func getUrlRespJson_async(httpMethod:Alamofire.Method, url:String, parameters: [String : AnyObject]? = nil, headers: [String : String]? = nil ) -> Alamofire.Result<JSON, NSError> {
</code>中，最后想要去返回对应的result：
写成：
<code>func getUrlRespJson_async(httpMethod:Alamofire.Method, url:String, parameters: [String : AnyObject]? = nil, headers: [String : String]? = nil ) -> Alamofire.Result<JSON, NSError> {
Alamofire
.request(
httpMethod,
url,
parameters: parameters,
encoding: ParameterEncoding.JSON,
headers: currentHeaders)
.responseJSON(completionHandler: { response in
switch response.result {
case .Success(let value):
let valueJson = JSON(value)
if let code = valueJson["code"].int {
if code == 200 {
if let dataDict = valueJson["data"].dictionary {
//maybe empty/int/json/...
let dataJson = JSON(dataDict)
gLog.verbose("dataJson=\(dataJson)")
return Alamofire.Result.Success(dataJson)
}
</code>结果出错：
Cannot convert call result type ‘Result<_, _>’ to expected type ‘Void’ (aka ‘()’)
Cannot convert call result type ‘Result<_, _>’ to expected type ‘Void’ (aka ‘()’)
Cannot convert call result type Result<_, _> to expected type
参考：
A Swifter Way Of Handling Errors | Jens Ravens
要不去，自己手动创建一个：
结果用：
<code>enum HttpResult<T> {
case Success(T)
case Error(NSError)
}
func getUrlRespJson_async(httpMethod:Alamofire.Method, url:String, parameters: [String : AnyObject]? = nil, headers: [String : String]? = nil ) -> HttpResult<JSON> {
//let dataJson = JSON(dataDict)
let dataJson:JSON = JSON(dataDict)
gLog.verbose("dataJson=\(dataJson)")
return HttpResult.Success(dataJson)
</code>竟然还是同样错误：
Cannot convert call result type ‘HttpResult<_>’ to expected type ‘Void’ (aka ‘()’)
swift generic type
swift generic type result
The Swift Programming Language (Swift 2.2): Generics
Generics in Swift, Part 2 · Episteme and Techne
Introduction to Swift Generics
Swift Tutorial: Introduction to Generics
后来发现是自己的函数写错了：
是写在了Alamofire的response的completionHandler部分
－》其是属于返回为空的
－》可以通过定义看出：
<code> public func responseJSON(queue queue: dispatch_queue_t? = default, options: NSJSONReadingOptions = default, completionHandler: Alamofire.Response<AnyObject, NSError> -> Void) -> Self </code>
－》completionHandler是个闭包的代码段
得到的值是：
Alamofire.Response<AnyObject, NSError>
此处拿到的是response那个值
对应的返回值是：Void，即无返回值
－》所以此处返回了Alamofire.Result的变量，才出错的
—》对于：
<code>func getUrlRespJson_async(httpMethod:Alamofire.Method, url:String, parameters: [String : AnyObject]? = nil, headers: [String : String]? = nil ) -> Alamofire.Result<JSON, NSError> {
Alamofire
.request(
httpMethod,
url,
parameters: parameters,
encoding: ParameterEncoding.JSON,
headers: currentHeaders)
.responseJSON(completionHandler: { response in
。。。
return Alamofire.Result.Success(dataJson)
</code>所以才出错的
应该改为：
<code>func getUrlRespJson_async(httpMethod:Alamofire.Method, url:String, parameters: [String : AnyObject]? = nil, headers: [String : String]? = nil ) -> Alamofire.Result<JSON, NSError> {
Alamofire
.request(
httpMethod,
url,
parameters: parameters,
encoding: ParameterEncoding.JSON,
headers: currentHeaders)
.responseJSON(completionHandler: { response in
。。。
}
return Alamofire.Result.Success(dataJson)
}
</code>就可以了
->但是此处不是同步的函数，是async的异步函数，所以实际上去改为：
<code> func getUrlRespJson_async(httpMethod:Alamofire.Method, url:String, parameters: [String : AnyObject]? = nil, headers: [String : String]? = nil, respJsonHandler: (Alamofire.Result<JSON, NSError>)-> Void) {
Alamofire
.request(
httpMethod,
url,
parameters: parameters,
encoding: ParameterEncoding.JSON,
headers: currentHeaders)
.responseJSON(completionHandler: { response in
switch response.result {
case .Success(let value):
let valueJson = JSON(value)
if let code = valueJson["code"].int {
if code == 200 {
if let dataDict = valueJson["data"].dictionary {
let dataJson:JSON = JSON(dataDict)
respJsonHandler(Alamofire.Result.Success(dataJson))
} else {
let emptyDataJson = JSON("")
respJsonHandler(Alamofire.Result.Success(emptyDataJson))
}
} else {
}
}
case .Failure(let error):
}
})
</code>就可以了。
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