ios - Swift 3 DispatchQueue.global (download images from Firebase and UI frozen) -


i have problema method:

func downloadimages(uid: string, indice: int) {         dispatchqueue.global(qos: .background).async {         let refbbdd = firdatabase.database().reference().child("users").child(uid)         refbbdd.observesingleevent(of: .value, with: { snapshot in             let snapshotvalue = snapshot.value as? nsdictionary             let profileimageurl = snapshotvalue?.value(forkey: "profileimageurl") as! string              let storage = firstorage.storage()             var reference: firstoragereference!              if(profileimageurl == "") {                 return             }             print("before")              reference = storage.reference(forurl: profileimageurl)             reference.downloadurl { (url, error) in                 let data = nsdata(contentsof: url!)                 let image = uiimage(data: data! data)                  print("image yet dowload ")                 self.citas[indice].image = image                  dispatchqueue.main.async(execute: { () -> void in                     self.tableview.reloadrows(at: [indexpath(row: indice, section: 0)], with: .none)                     //self.tableview.reloaddata()                     print("image loaded")                 })             }             print("after")         })     } }

i want download images in background mode. want follow using app, ui has frozen until methods not entry in reloadrows.

is possible run in true background mode , can follow using app??

trace program: 

before after before after ... before after before after image yet dowload  --> here start ui frozen image loaded image yet dowload  image yet dowload  ... image yet dowload  image yet dowload  image loaded   image loaded ... image loaded image loaded image yet dowload ------> here ui not frozen image loaded

the problem caused line: let data = nsdata(contentsof: url!). constructor of nsdata should used read contents of local url (a file path on ios device), since synchronous method , hence if call download file url, blocking ui long time.

i have never used firebase, looking @ documentation, seems me using wrong method download file. should using func getdata(maxsize size: int64, completion: @escaping (data?, error?) -> void) -> storagedownloadtask instead of func downloadurl(completion: @escaping (url?, error?) -> void), since documentation states, latter "retrieves long lived download url revokable token", doesn't download contents of url itself.

moreover, shouldn't force unwrapping values in completion handler of network request. network requests can fail reasons other programming error, if don't handle errors gracefully, program crash.


Comments

Post a Comment

Popular posts from this blog

neo4j - finding mutual friends in a cypher statement starting with three or more persons -

Image
i trying build cypher statement neo4j know 2-n starting nodes name , need find node (if any) can reached of starting nodes. at first tought similar "mutual friend" situation handled (start1)-[*..2]->(main)<-[*..2]-(start2) in case have more 2 starting points around 6 know name. so puzzled how can include third, fourth , on node cypher able find commmon root amongst them. in above example neo4j website need path starting 'dilshad', 'becky' , 'cesar' check if have common friend (anders) excluding 'filipa' , 'emil' not friends of three. so far create statement programmatically looks like match (start1 {name:'person1'}), (start2 {name:'person2'}), (start3 {name: 'person3'}), (main) (start1)-[*..2]->(main) , (start2)-[*..2]->(main) , (start3)-[*..2]->(main) return distinct main but wondering if there more elegant / efficient way in cypher possibly use list of names parameter ...
Read more

php - How to remove letter in front of the word laravel -

Image
based on picture above result of var_dump() , dd() of same variable ,when var_dump() , apostrophe (') symbol in black diamond of question mark , when dd() same variable , apostrophe can seen letter 'b' appear in front of words what want can me result : loreal's sdn bhd and @ same time want remove special character ( excluding these 4 symbols (-) ,(_) ,('),(,) ) simply escape special character resolve issue. mysqli_real_escape_string resolve issue. $name = mysqli_real_escape_string($request()->user); or use addslashes function() $name = addslashes($request()->user);
Read more

minify - Minimizing css files -

i want know how css files can minimized. currently, using external sites css minifier compress css files. however, after removing whitespaces, comments, etc, file sizes reduced 10-15%. how frameworks bootstrap manage make minimized versions kilobytes. as example, css is: body { background-color: #ff0; } the reduction goes 28 bytes 22 bytes other css files have lot more characters still smaller this. actually minifying code means it's remove thing code white space characters new line characters comments block delimiters it reduces amount of code has transferred on web , speed site load fastly.but unreadable format.
Read more