ios - Swift - Method chaining -

i'd implement method chaining in swift code, alamofire methods. example, if have use function below

getlistforid(12).success {    // success block }. failure {    // failure block } 

how create function getlistforid?

to expand on great points @dasblinkenlight , @sulthan have made – here's small example of how achieve request function take success , failure closure, in convenient syntax want.

first, you'll have define new class represent 'result handler'. success , failure functions pass around, allowing add multiple trailing closures make completion block logic. you'll want this:

class resulthandler {      typealias successclosure = requesthandler.output->void     typealias failureclosure = void->void      // success , failure callback arrays     private var _successes = [successclosure]()     private var _failures = [failureclosure]()      /// invoke stored callbacks given callback result     func invokecallbacks(result:requesthandler.result) {          switch result {             case .success(let output): _successes.foreach{$0(output)}             case .failure: _failures.foreach{$0()}         }     }      // remove callbacks – call within invokecallbacks     // depending on re-usability of class     func removeallcallbacks() {         _successes.removeall()         _failures.removeall()     }      /// appends new success callback result handler's successes array     func success(closure:successclosure) -> self {         _successes.append(closure)         return self     }      /// appends new failure callback result handler's failures array     func failure(closure:failureclosure) -> self {         _failures.append(closure)         return self     } } 

this allow define multiple success or failure closures executed on completion. if don't need capacity multiple closures, can simplify class down stripping out arrays – , keeping track of last added success , failure completion blocks instead.

now have define function generates new resulthandler instance , given asynchronous request, invokecallbacks method being invoked upon completion:

func dorequest(input:input) -> resulthandler {     let resulthandler = resulthandler()     dosomethingasynchronous(resulthandler.invokecallbacks)     return resulthandler } 

now can call this:

dorequest(input).success {result in     print("success, with:", result) }.failure {     print("fail :(") } 

the thing note dosomethingasynchronous function have dispatch completion block main thread, ensure thread safety.

---

full project (with added example on usage): https://github.com/originaluser2/callback-closure-chaining