swift - a function does internet fetching and return a value -


i know following piece of code wrong, want show intent. want write method called multiple times. , fetching method tell me if reached.

func fetch(url: string) -> bool? {     let defaultsession = urlsession(configuration: urlsessionconfiguration.default)     let url = url(string: url)     var bool: bool? = nil     if let url = url {         defaultsession.datatask(with: url, completionhandler: { data, response, error in             if let error = error {                 print(error)                 return             }             dispatchqueue.main.async {                 if let httpresponse = response as? httpurlresponse, 200...299 ~= httpresponse.statuscode, let data = data {                     // handle data.                     bool = true                 } else {                     print("something wrong")                     bool = false                 }             }         }).resume()     }     return bool }  if let bool = fetch(url: "https://www.google.com.hk/webhp?hl=en&sa=x&ved=0ahukewimubk7r-hvahvfmzqkhazmammqpagd"), bool == true {     // if true, can go next step. }

making ui wait on completion of api call not recommended. app have no control on how long api call take. situations bad network connectivity can take several seconds respond.

you can handle situation use completion handler.

func fetch(url: string, completion: @escaping (_ success: bool) -> void) {     let defaultsession = urlsession(configuration: urlsessionconfiguration.default)     let url = url(string: url)      if let url = url {         defaultsession.datatask(with: url, completionhandler: { data, response, error in             if let error = error {                 print(error)                 return             }              if let httpresponse = response as? httpurlresponse, 200...299 ~= httpresponse.statuscode, let data = data {                 // handle data.                 completion(true)             } else {                 print("something wrong")                 completion(false)             }         }).resume()     } }   func testfetch () {     fetch(url: "https://www.google.com.hk/webhp?hl=en&sa=x&ved=0ahukewimubk7r-hvahvfmzqkhazmammqpagd") { (success) in             // if true, can go next step.         dispatchqueue.main.async {             if success {                 //             }             else {                 // not             }         }     } }

Comments

Post a Comment

Popular posts from this blog

What is happening when Matlab is starting a "parallel pool"? -

running parallel cpu processes in matlab starts command parpool() according documentation , function: [creates] special job on pool of workers, , [connects] matlab client parallel pool. this function takes bit of time execute, on order of 30 seconds. in other multi-cpu paradigms openmp, parallel execution seems totally transparent -- i've never noticed behavior analogous matlab (granted i'm not experienced parallel programming). so, happening between time parpool() called , when finishes executing? takes long? parallel computing toolbox enables run matlab code in parallel using several different paradigms (e.g. jobs , tasks, parfor , spmd , parfeval , batch processing), , run either locally (parallelised across cores in local machine) or remotely (parallelised across machines in cluster - either 1 own, or 1 in cloud). in of these cases, code run on matlab workers , copies of matlab without interactive desktop. if you're intending run on remo...
Read more

angular - DownloadURL return null in below code -

when change file updated in firebase storage when try downloadurl show null. filechange(event: any) { const imagefolder: string = this.employee.id; const filelist: filelist = event.target.files; const file: file = filelist[0]; const storageref = firebase.storage().ref().child(`${imagefolder}/profile.jpg`).put(file); console.log(storageref.snapshot.downloadurl); } the put() asynchronous. if want url after file uploaded have this: firebase.storage().ref().child(`${imagefolder}/profile.jpg`).put(file).then((snapshot) => { storageref = snapshot.downloadurl: console.log(snapshot.downloadurl); });
Read more

php - Cannot override Laravel Spark authentication with own implementation -

during login process of laravel spark need request token of remote api. api stores exact same users , passwords laravel spark application. therefore need username , non hashed password of user during authentication process. i thought overriding authenticated method solution problem. in routes/web.php override post /login endpoint , pointing endpoint own logincontroller: <?php namespace app\http\controllers\auth; use illuminate\support\facades\log; use illuminate\http\request; use laravel\spark\http\controllers\auth\logincontroller sparklogincontroller; class logincontroller extends sparklogincontroller { /** * create new login controller instance. * * @return void */ public function __construct() { parent::__construct(); } /** * handle successful authentication attempt. * * @param request $request * @param \illuminate\contracts\auth\authenticatable $user * @return response */ public fu...
Read more