How to use block/closure in swift - ios

Question

In one of my app I have used block for webservice calling and getting response. Now I want to write this app in swift, but I am getting trouble to use blocks/Closure in Swift.
Here is my objective C code which I want to migrate in swift:
calling a class method of Communicator
[[Communicator sharedInstance]callWebService:WS_LOGIN withMethod:POST_METHOD andParams:params showLoader:YES completionBlockSuccess:^(id obj) {
//Do play with data
}completionBlockFailiure:^(id obj) {
//Show alert with error
}];
in communicator class
-(void)callWebService:(NSString *)serviceName withMethod:(NSString *)methodName andParams:(NSDictionary *)params showLoader:(BOOL)showLoader completionBlockSuccess:(void (^)(id))aBlock completionBlockFailiure:(void (^)(id))aFailBlock
{
if (showLoader) {
// show loader
}
[self performRequestWithServiceName:serviceName method:methodName andParams:params successblock:aBlock failureblock:aFailBlock];
}
- (void)performRequestWithServiceName:(NSString *)serviceName method:(NSString*)methodName andParams:(NSDictionary*)params
successblock:(void (^)(id obj))successBlock
failureblock:(void (^)(id obj))failBlock {
if(callSuceess){
successBlock(#"Success");
}else{
successBlock(nil);
}
}

Answer 1

For Swift. Use AnyObject for id objc type.
func callWebservice (serviceName: String, withMethod method: String, andParams params: NSDictionary, showLoader loader: Bool, completionBlockSuccess aBlock: ((AnyObject) -> Void), andFailureBlock failBlock: ((AnyObject) -> Void)) {
if loader {
// Show loader
}
performRequestWithServiceName(serviceName, method: method, andParams: params, success: aBlock, failure: failBlock)
}
func performRequestWithServiceName(serviceName: String, method methodName: String, andParams params: NSDictionary, success successBlock: ((AnyObject) -> Void), failure failureBlock: ((AnyObject) -> Void)) {
if callSuceess {
successBlock("Success")
}else {
successBlock(nil)
}
}
UPDATE: An example when you want call web service. See code below
callWebservice("your-service-name", withMethod: "your-method", andParams: ["your-dic-key": "your dict value"], showLoader: true/*or false*/, completionBlockSuccess: { (success) -> Void in
// your successful handle
}) { (failure) -> Void in
// your failure handle
}

Answer 2

Your code might look like this:
func callWebService(serviceName: String, method: String, params: [String : AnyObject], showLoader: Bool, success: (responseObject: AnyObject) -> Void, failure: (responseObject: AnyObject) -> Void) {
if showLoader {
// show loader
}
performRequest(serviceName, method: method, params: params, success: success, failure: failure)
}
func performRequest(serviceName: String, method: String, params: [String : AnyObject], success: (responseObject: AnyObject) -> Void, failure: (responseObject: AnyObject) -> Void) {
}
I replaced NSDictionary with [String : AnyObject]. If you can replace any of the uses of AnyObject with more specific types, your code will be cleaner and more stable.

Answer 3

For Swift Closures we have to use ( ) -> ( )
For example:
func yourFunction(success: (response: AnyObject!) -> Void, failure: (error: NSError?) -> Void) {
}
You can call it as:
yourFunction({(response) -> Void in
// Success
}) { (error) -> Void in
// Handle Errors
}
Hope it will help you to create Closures with your requirements.

Answer 4

In the communicator class the method that cals the webservice would be defined something like this depending on the type of object you want to return
func performRequest(serviceName: NSString, methodName: NSString,paramaters:NSDictionary, successblock: (String)->(), failureBlock: () -> ()) {
if(callSuccess) {
successblock("Success")
} else {
failureBlock()
}
We define the success and failure blocks types as by their function signatures in the case above success is defined as a method that takes a string as an input parameter and returns nothing so we can then call successBlock passing in a string. The failure block is defined above as a block that takes no parameters and returns nothing.
To call this method
func callWebService(serviceName: NSString, method: NSString and parameters: NSDictionary, showLoader: Bool, completionBlockSuccess:(String) -> (), completionBlockFailiure:() -> ()) {
if (showLoader) {
// show loader
}
performRequest(serviceName: serviceName, methodName: method, parameters, successBlock:completionBlockSuccess, failureBlock: completionBlockFailiure)
}
Finally to call this
Communicator.sharedInstance().callWebService(serviceName: WS_LOGIN , method: POST_METHOD and parameters: params, showLoader: true, completionBlockSuccess:{ returnedString in
//Do play with data
}, completionBlockFailiure:{
//Show alert with error
})
For the completion block we define a variable returnedString to allow us to manipulate that input parameter (in the above example it would be the string "Success"). I assume your data is not just returning a string though so you will probably need to play around with they type depending on what your service returns.
Also here I tried to match your method signatures by using NSString and NSDictionary though depending on your needs the Swift equivalents String and [String: AnyObject] could be more appropriate.

Answer 5

func processingWithAnyObject(input: String, completion: #escaping (_ result: AnyObject) -> Void) {
...
completion(response.result.value! as AnyObject)
}
processingWithAnyObject("inputString") {
(result: AnyObject) in
print("back to caller: \(result)")
}