How to Stop UI thread until Network Thread Completes? - ios

Question

I am displaying some data from JSON into my AccordionView. The problem is that my View thread completes executing before my Network Thread. So I Can't populate the Data which I get from the Array to my AccordionView.
So it shows that Array index out of range exception. I also tried using the reloadData Method But it is of no use.
I researched this issue and found about GCD. I can't figure out how to use GCD for this issue.
This is the AccordionView Library.
import UIKit
import Alamofire
import SwiftyJSON
var CourseIdinController : String!
var CourseDescriptionC: String!
var ChapNameC : [String] = []
var titleLabel : UILabel?
class CoursePageController: UIViewController {
#IBOutlet weak var courseDesc: UITextView!
var CourseName : String!
var ChapName : [String] = []
var LessonName : [String] = []
var myAccordionView : MKAccordionView?
override func viewDidLoad() {
super.viewDidLoad()
self.title = CourseName
self.courseDesc.text = CourseDescriptionC
self.courseDesc.setContentOffset(CGPointZero, animated: true)
view.bounds.size.height = 450.0
myAccordionView = MKAccordionView(frame: CGRectMake(0, 111, CGRectGetWidth(view.bounds), CGRectGetHeight(view.bounds)));
println(ChapNameC.count)
myAccordionView!.delegate = self;
myAccordionView!.dataSource = self;
view.addSubview(myAccordionView!);
getData()
getlData()
}
func getData(){
Alamofire.request(.GET, "http://www.wgve.com/index.php/capp/get_chapter_by_course_id/\(CourseIdinController)")
.responseJSON { (_, _, data, _) in
let json = JSON(data!)
let catCount = json.count
for index in 0...catCount-1 {
let cname = json[index]["CHAPTER_NAME"].string
self.ChapName.append(cname!)
println(self.ChapName[index])
}
self.myAccordionView!.tableView?.reloadData()
}}
func getlData(){
Alamofire.request(.GET, "http://www.wgve.com/index.php/capp/get_lesson_by_course_id/\(CourseIdinController)")
.responseJSON { (_, _, data, _) in
let json = JSON(data!)
let catCount = json.count
for index in 0...catCount-1 {
let cname = json[index]["LESSON_NAME"].string
self.LessonName.append(cname!)
}
self.myAccordionView!.tableView?.reloadData()
}}
func accordionView(accordionView: MKAccordionView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell : UITableViewCell? = UITableViewCell(style: UITableViewCellStyle.Subtitle, reuseIdentifier: nil)
//cell?.imageView = UIImageView(image: UIImage(named: "lightGrayBarWithBluestripe"))
// Background view
var bgView : UIView? = UIView(frame: CGRectMake(0, 0, CGRectGetWidth(accordionView.bounds), 50))
var bgImageView : UIImageView! = UIImageView(image: UIImage(named: "lightGrayBarWithBluestripe"))
bgImageView.frame = (bgView?.bounds)!
bgImageView.contentMode = UIViewContentMode.ScaleToFill
bgView?.addSubview(bgImageView)
cell?.backgroundView = bgView
// You can assign cell.selectedBackgroundView also for selected mode
cell?.textLabel?.text = LessonName[0]
return cell!
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
// MARK: - Implemention of MKAccordionViewDatasource method
extension CoursePageController : MKAccordionViewDatasource {
func numberOfSectionsInAccordionView(accordionView: MKAccordionView) -> Int {
println(ChapName.count)
return ChapName.count
}
func accordionView(accordionView: MKAccordionView, numberOfRowsInSection section: Int) -> Int {
println(LessonName.count)
return LessonName.count
}
}
// MARK: - Implemention of MKAccordionViewDatasource method
extension CoursePageController : MKAccordionViewDatasource {
func numberOfSectionsInAccordionView(accordionView: MKAccordionView) -> Int {
return ChapName.count
}
func accordionView(accordionView: MKAccordionView, numberOfRowsInSection section: Int) -> Int {
return LessonName.count
}
}
// MARK: - Implemention of MKAccordionViewDelegate method
extension CoursePageController : MKAccordionViewDelegate {
func accordionView(accordionView: MKAccordionView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
return 50
}
func accordionView(accordionView: MKAccordionView, heightForHeaderInSection section: Int) -> CGFloat {
return 50
}
func accordionView(accordionView: MKAccordionView, viewForHeaderInSection section: Int, isSectionOpen sectionOpen: Bool) -> UIView? {
var view : UIView! = UIView(frame: CGRectMake(0, 0, CGRectGetWidth(accordionView.bounds), 50))
// Background Image
var bgImageView : UIImageView = UIImageView(frame: view.bounds)
bgImageView.image = UIImage(named: ( sectionOpen ? "grayBarSelected" : "grayBar"))!
view.addSubview(bgImageView)
// Arrow Image
var arrowImageView : UIImageView = UIImageView(frame: CGRectMake(15, 15, 20, 20))
arrowImageView.image = UIImage(named: ( sectionOpen ? "close" : "open"))!
view.addSubview(arrowImageView)
// Title Label
titleLabel = UILabel(frame: CGRectMake(50, 0, CGRectGetWidth(view.bounds) - 120, CGRectGetHeight(view.bounds)))
if (ChapName.count != 0) {
let count = ChapName.count
for index in 0...count-1 {
titleLabel!.text = self.ChapName[index]
}
}
titleLabel!.textColor = UIColor.whiteColor()
view.addSubview(titleLabel!)
return view
}
}
Note:
It shows me error because the ChapName & lesson name array are Empty. If i Hardcode the values. It prints both the array's in my console.
May be the accordionView doesn't support the reload Method?
or Where am I Going Wrong ?
UPDATE
numberOfSectionsInAccordionView throws Error like this fatal error: Can't form Range with end < start which on line 233
Refer this link
2.The titleLabel returns only the last item in the Array. I don't know Why ?

Answer 1

You should make sure all your json data is successfully stored into an array "accordionDataArray" before you attempt to reload it.
ATTENTION : make sure that the datasource methods numberOfRowsInSection and numberOfSectionsInAccordionView rely on the accordionDataArray content (or whatever Array you have) to determine the number of sections and rows of the accordion.
P.S. Anyway Why would you reload the content of the accordion in a loop?
Do this instead:
for index in 0...catCount-1 {
let cname = json[index]["CHAPTER_NAME"].string
self.ChapName.append(cname!)
println(self.ChapName[index])
}
self.myAccordionView!.tableView?.reloadData()
UPDATE:
To get passed the fact that ChapName & lessonName array are asked for some value when they are Empty , you need to check that like this whenever they occur:
if (ChapName.count != 0) {
titleLabel!.text = self.ChapName[0]
}
if (LessonName.count != 0){
// do something
}
Make sure you update your code and test. In the method:
func accordionView(accordionView: MKAccordionView, viewForHeaderInSection section: Int, isSectionOpen sectionOpen: Bool) -> UIView? {
[...]
if (ChapName.count != 0) {
titleLabel!.text = self.ChapName[0]
}
[...]
}
UPDATE 2: The library you are using doesn't seem to allow the number of sections to be 0. I suggest you contact the library's owner if you can't make sure that the number of section is at least 1.
Regarding to your other issue with titleLabel being always the last item of the array you need to change this:
if (ChapName.count != 0) {
let count = ChapName.count
for index in 0...count-1 {
titleLabel!.text = self.ChapName[index]
}
}
into this:
titleLabel!.text = self.ChapName[section]

Answer 2

About why the code above does not work:
numberOfRowsInSection returns a hardcoded value, regardless of the JSON response.
About stopping the UI thread:
We are somewhat glad you can't do that. GCD helps you to share processor time efficiently, the exact opposite of holding the UI thread hostage. Image the consequence if somehow your network thread would hang. What would happen to the UI thread? Don't do it.
Solutions: Your make your UI thread clever enough to handle absence of datum. i.e. do not return hardcoded counts for sections or cells. When you receive data, update your records (the model), send a refresh message to the UI (such as reloadData in UITableView).