POST 中的 HTTP POST 错误处理 2
HTTP POST error Handling in Swift 2
我是新来的,这是我的第一个问题...
我尝试在 Swift 2 中编写一个发出 HTTP POST 请求的应用程序,但我不知道如何使用 Swift 2 的新错误处理。谁能告诉我如何在下面的代码片段中实现 Swift 2 的“do-try-catch”错误处理?
(此代码片段使用 swift 1.2 的旧错误处理)
func post(params : Dictionary<String, String>, url : String) {
var request = NSMutableURLRequest(URL: NSURL(string: url)!)
var session = NSURLSession.sharedSession()
request.HTTPMethod = "POST"
var err: NSError?
request.HTTPBody = NSJSONSerialization.dataWithJSONObject(params, options: nil/*, error: &err*/)
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
var task = session.dataTaskWithRequest(request, completionHandler: {data, response, error -> Void in
print("Response: \(response)")
var strData = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Body: \(strData)")
var err: NSError?
var json = NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves/*, error: &err*/) as? NSDictionary
// Did the JSONObjectWithData constructor return an error? If so, log the error to the console
if(err != nil) {
print(err!.localizedDescription)
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
}
else {
// The JSONObjectWithData constructor didn't return an error. But, we should still
// check and make sure that json has a value using optional binding.
if let parseJSON = json {
// Okay, the parsedJSON is here, let's get the value for 'success' out of it
var success = parseJSON["success"] as? Int
print("Succes: \(success)")
}
else {
// Woa, okay the json object was nil, something went worng. Maybe the server isn't running?
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: \(jsonStr)")
}
}
})
task!.resume()
}
一般来说,如果一个函数 throws
你必须将它写在 do catch
块中或者只是将外部作用域函数(在本例中 post
)标记为 throws
:
func post(params : Dictionary<String, String>, url : String) {
let request = NSMutableURLRequest(URL: NSURL(string: url)!)
let session = NSURLSession.sharedSession()
request.HTTPMethod = "POST"
do {
request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: .PrettyPrinted)
} catch {
//handle error. Probably return or mark function as throws
print(error)
return
}
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
let task = session.dataTaskWithRequest(request, completionHandler: {data, response, error -> Void in
// handle error
guard error == nil else { return }
print("Response: \(response)")
let strData = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Body: \(strData)")
let json: NSDictionary?
do {
json = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves) as? NSDictionary
} catch let dataError {
// Did the JSONObjectWithData constructor return an error? If so, log the error to the console
print(dataError)
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
// return or throw?
return
}
// The JSONObjectWithData constructor didn't return an error. But, we should still
// check and make sure that json has a value using optional binding.
if let parseJSON = json {
// Okay, the parsedJSON is here, let's get the value for 'success' out of it
let success = parseJSON["success"] as? Int
print("Succes: \(success)")
}
else {
// Woa, okay the json object was nil, something went worng. Maybe the server isn't running?
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: \(jsonStr)")
}
})
task!.resume()
}
如果您不想在 post
函数中直接处理这些错误,您可以将其声明为 throws
而根本不必使用 do catch
您可能希望将 NSJSONSerialization
调用包装在 do
/try
/catch
逻辑中,如下所示。
在Swift 3:
var request = URLRequest(url: URL(string: urlString)!)
let session = URLSession.shared
request.httpMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.httpBody = try! JSONSerialization.data(withJSONObject: parameters)
// or if you think the conversion might actually fail (which is unlikely if you built `parameters` yourself)
//
// do {
// request.httpBody = try JSONSerialization.data(withJSONObject: parameters)
// } catch {
// print(error)
// }
let task = session.dataTask(with: request) { data, response, error in
guard let data = data, error == nil else {
print("error: \(error)")
return
}
// this, on the other hand, can quite easily fail if there's a server error, so you definitely
// want to wrap this in `do`-`try`-`catch`:
do {
if let json = try JSONSerialization.jsonObject(with: data) as? [String: Any] {
let success = json["success"] as? Int // Okay, the `json` is here, let's get the value for 'success' out of it
print("Success: \(success)")
} else {
let jsonStr = String(data: data, encoding: .utf8) // No error thrown, but not dictionary
print("Error could not parse JSON: \(jsonStr)")
}
} catch let parseError {
print(parseError) // Log the error thrown by `JSONObjectWithData`
let jsonStr = String(data: data, encoding: .utf8)
print("Error could not parse JSON: '\(jsonStr)'")
}
}
task.resume()
或者,在 Swift 2
let request = NSMutableURLRequest(URL: NSURL(string: urlString)!)
let session = NSURLSession.sharedSession()
request.HTTPMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.HTTPBody = try! NSJSONSerialization.dataWithJSONObject(parameters, options: [])
// or if you think the conversion might actually fail (which is unlikely if you built `parameters` yourself)
//
// do {
// request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: [])
// } catch {
// print(error)
// }
let task = session.dataTaskWithRequest(request) { data, response, error in
guard let data = data where error == nil else {
print("error: \(error)")
return
}
// this, on the other hand, can quite easily fail if there's a server error, so you definitely
// want to wrap this in `do`-`try`-`catch`:
do {
if let json = try NSJSONSerialization.JSONObjectWithData(data, options: []) as? NSDictionary {
let success = json["success"] as? Int // Okay, the `json` is here, let's get the value for 'success' out of it
print("Success: \(success)")
} else {
let jsonStr = String(data: data, encoding: NSUTF8StringEncoding) // No error thrown, but not NSDictionary
print("Error could not parse JSON: \(jsonStr)")
}
} catch let parseError {
print(parseError) // Log the error thrown by `JSONObjectWithData`
let jsonStr = String(data: data, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
}
}
task.resume()
我还建议对 data
的强制展开更加小心,因为您想要 detect/handle 错误,而不是崩溃。例如,上面我使用 guard
语句来解包它。
我是新来的,这是我的第一个问题... 我尝试在 Swift 2 中编写一个发出 HTTP POST 请求的应用程序,但我不知道如何使用 Swift 2 的新错误处理。谁能告诉我如何在下面的代码片段中实现 Swift 2 的“do-try-catch”错误处理? (此代码片段使用 swift 1.2 的旧错误处理)
func post(params : Dictionary<String, String>, url : String) {
var request = NSMutableURLRequest(URL: NSURL(string: url)!)
var session = NSURLSession.sharedSession()
request.HTTPMethod = "POST"
var err: NSError?
request.HTTPBody = NSJSONSerialization.dataWithJSONObject(params, options: nil/*, error: &err*/)
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
var task = session.dataTaskWithRequest(request, completionHandler: {data, response, error -> Void in
print("Response: \(response)")
var strData = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Body: \(strData)")
var err: NSError?
var json = NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves/*, error: &err*/) as? NSDictionary
// Did the JSONObjectWithData constructor return an error? If so, log the error to the console
if(err != nil) {
print(err!.localizedDescription)
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
}
else {
// The JSONObjectWithData constructor didn't return an error. But, we should still
// check and make sure that json has a value using optional binding.
if let parseJSON = json {
// Okay, the parsedJSON is here, let's get the value for 'success' out of it
var success = parseJSON["success"] as? Int
print("Succes: \(success)")
}
else {
// Woa, okay the json object was nil, something went worng. Maybe the server isn't running?
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: \(jsonStr)")
}
}
})
task!.resume()
}
一般来说,如果一个函数 throws
你必须将它写在 do catch
块中或者只是将外部作用域函数(在本例中 post
)标记为 throws
:
func post(params : Dictionary<String, String>, url : String) {
let request = NSMutableURLRequest(URL: NSURL(string: url)!)
let session = NSURLSession.sharedSession()
request.HTTPMethod = "POST"
do {
request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: .PrettyPrinted)
} catch {
//handle error. Probably return or mark function as throws
print(error)
return
}
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
let task = session.dataTaskWithRequest(request, completionHandler: {data, response, error -> Void in
// handle error
guard error == nil else { return }
print("Response: \(response)")
let strData = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Body: \(strData)")
let json: NSDictionary?
do {
json = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves) as? NSDictionary
} catch let dataError {
// Did the JSONObjectWithData constructor return an error? If so, log the error to the console
print(dataError)
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
// return or throw?
return
}
// The JSONObjectWithData constructor didn't return an error. But, we should still
// check and make sure that json has a value using optional binding.
if let parseJSON = json {
// Okay, the parsedJSON is here, let's get the value for 'success' out of it
let success = parseJSON["success"] as? Int
print("Succes: \(success)")
}
else {
// Woa, okay the json object was nil, something went worng. Maybe the server isn't running?
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: \(jsonStr)")
}
})
task!.resume()
}
如果您不想在 post
函数中直接处理这些错误,您可以将其声明为 throws
而根本不必使用 do catch
您可能希望将 NSJSONSerialization
调用包装在 do
/try
/catch
逻辑中,如下所示。
在Swift 3:
var request = URLRequest(url: URL(string: urlString)!)
let session = URLSession.shared
request.httpMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.httpBody = try! JSONSerialization.data(withJSONObject: parameters)
// or if you think the conversion might actually fail (which is unlikely if you built `parameters` yourself)
//
// do {
// request.httpBody = try JSONSerialization.data(withJSONObject: parameters)
// } catch {
// print(error)
// }
let task = session.dataTask(with: request) { data, response, error in
guard let data = data, error == nil else {
print("error: \(error)")
return
}
// this, on the other hand, can quite easily fail if there's a server error, so you definitely
// want to wrap this in `do`-`try`-`catch`:
do {
if let json = try JSONSerialization.jsonObject(with: data) as? [String: Any] {
let success = json["success"] as? Int // Okay, the `json` is here, let's get the value for 'success' out of it
print("Success: \(success)")
} else {
let jsonStr = String(data: data, encoding: .utf8) // No error thrown, but not dictionary
print("Error could not parse JSON: \(jsonStr)")
}
} catch let parseError {
print(parseError) // Log the error thrown by `JSONObjectWithData`
let jsonStr = String(data: data, encoding: .utf8)
print("Error could not parse JSON: '\(jsonStr)'")
}
}
task.resume()
或者,在 Swift 2
let request = NSMutableURLRequest(URL: NSURL(string: urlString)!)
let session = NSURLSession.sharedSession()
request.HTTPMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.HTTPBody = try! NSJSONSerialization.dataWithJSONObject(parameters, options: [])
// or if you think the conversion might actually fail (which is unlikely if you built `parameters` yourself)
//
// do {
// request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: [])
// } catch {
// print(error)
// }
let task = session.dataTaskWithRequest(request) { data, response, error in
guard let data = data where error == nil else {
print("error: \(error)")
return
}
// this, on the other hand, can quite easily fail if there's a server error, so you definitely
// want to wrap this in `do`-`try`-`catch`:
do {
if let json = try NSJSONSerialization.JSONObjectWithData(data, options: []) as? NSDictionary {
let success = json["success"] as? Int // Okay, the `json` is here, let's get the value for 'success' out of it
print("Success: \(success)")
} else {
let jsonStr = String(data: data, encoding: NSUTF8StringEncoding) // No error thrown, but not NSDictionary
print("Error could not parse JSON: \(jsonStr)")
}
} catch let parseError {
print(parseError) // Log the error thrown by `JSONObjectWithData`
let jsonStr = String(data: data, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
}
}
task.resume()
我还建议对 data
的强制展开更加小心,因为您想要 detect/handle 错误,而不是崩溃。例如,上面我使用 guard
语句来解包它。