How to code Nested Loop with synchronous in swift? - ios

Question

In my project, I call getMain() and that has nested loop. That loop call setUp(). My problem is setUp() before finish, upper loop is quit.
Firstly call getMian():
func getMain(){
let entityDescription = NSFetchRequest<NSFetchRequestResult>(entityName: "MainThemeHome")
do{
let results = try context.fetch(entityDescription)
if(results.count) > 0 {
sections.removeAll()
debugPrint(results.count)
outer_count = results.count
for i in 0 ..< (results.count){
let match = results[i] as! NSManagedObject
let associated_url = match.value(forKey: "main_associated_url") as! String
let name = match.value(forKey: "main_name") as! String
//call function
self.setUpViews(associated_url: associated_url, main_name: name, i: i )
self.myGroup.leave()
}
}else{
}
}catch{}
}
Loop call setUp() is below,
private func setUp(associated_url : String , main_name: String,i : Int) {
if Reachability().isInternetAvailable() == true {
self.rest.auth(auth: self.prefs.value(forKey: "access_token") as! String!)
self.rest.get(url: StringResource().mainURL + associated_url , parma: [ "show_min": "true" ], finished: {(result : NSDictionary, status : Int) -> Void in
self.assetsTable.removeAll()
if(status == 200){
let data = result["data"] as! NSArray
for item in 0…data.count - 1 {
let themes : AnyObject = data[item] as AnyObject
let created = themes["created"] as! String
let assets_id = themes["id"] as! Int
let name = themes["name"] as! String
var poster_img_url = themes["poster_image_url"] as! String
let provider_id = themes["provider_id"] as! Int
poster_img_url = StringResource().posterURL + poster_img_url
self.assetsTable.append(AssetsTableItem(created: created, assets_id: assets_id, name: name, poster_image_url: poster_img_url , provider_id: provider_id))
}
}
self.sections.append(SectionsHome(package_name: main_name, package_url: associated_url,i: i,packageTable: self.assetsTable))
self.inner_count = self.sections.count
}else{
}
})
}
}
How to control setUp() is completely finished, loop will be increase count and quit. How to solve this problem. Please help.

Answer 1

You need to use closures in setUp function so that when the setUp if finished you will get the callback
private func setUp(associated_url : String , main_name: String,i : Int, ,sucess:((Void) -> Void)?,failure:((Void?) -> Void)?) {
if Reachability().isInternetAvailable() == true {
self.rest.auth(auth: self.prefs.value(forKey: "access_token") as! String!)
self.rest.get(url: StringResource().mainURL + associated_url , parma: [ "show_min": "true" ], finished: {(result : NSDictionary, status : Int) -> Void in
self.assetsTable.removeAll()
if(status == 200){
let data = result["data"] as! NSArray
for item in 0…data.count - 1 {
let themes : AnyObject = data[item] as AnyObject
let created = themes["created"] as! String
let assets_id = themes["id"] as! Int
let name = themes["name"] as! String
var poster_img_url = themes["poster_image_url"] as! String
let provider_id = themes["provider_id"] as! Int
poster_img_url = StringResource().posterURL + poster_img_url
self.assetsTable.append(AssetsTableItem(created: created, assets_id: assets_id, name: name, poster_image_url: poster_img_url , provider_id: provider_id))
}
}
self.sections.append(SectionsHome(package_name: main_name, package_url: associated_url,i: i,packageTable: self.assetsTable))
self.inner_count = self.sections.count
sucess!()
}else{
failure!()
}
})
}
}
And change the way you call the function as
self.setUp(associated_url: associated_url, main_name: name, i: i, sucess: { () in
debugPrint("SUCCESS")
}) { () in
debugPrint("FAILURE")
}

Answer 2

What I can understand is that you want to make loop wait until the data is not fetched in that particular interation number. If this is the case then you should look for synchronous operation. Like dont let the control passed to next iteration until the operation is finished. But this is a bad practice and makes your app behaviour non responsive.
I would say to work on asynchronous line and create a block or closure and put your code what is expected to perform when you receive your data and put the code outside that block that are not dependent on the data. Blocks anyway capture the environment in that case you should not be worried about the control getting passed.