Load data in new view when button is clicked with swift

Question

I am developing an app, where I create buttons programmatically. When I click a button, it will request data from a database and show it in another view.

I use button.tag to determine what data to request, and I can only get the tag once the button is clicked.

However when I click the button, it shows nothing the first time. I must click it again to see the data which I want.

override func viewDidLoad() {
    super.viewDidLoad()

    //parseJSON(tagId)
    createButton()

    // Do any additional setup after loading the view, typically from a nib.
}
func createButton(){

   var j:CGFloat=60
    for var i:Int = 0 ; i < myImages.count;i = i+1 {
        let myButton = UIButton()
        myButton.setImage(UIImage(named: "carasusto.jpg"), forState: UIControlState.Normal)
        myButton.setTitleColor(UIColor.blueColor(), forState: .Normal)
        myButton.frame = CGRectMake(j, j+60, 50, 50)

        myButton.tag = i //assign a tag to every button
        myButton.addTarget(self, action: "segueToCreate:", forControlEvents: UIControlEvents.TouchUpInside)
        self.view.addSubview(myButton)

        j=j+60
        print(myImages[i])

    }
}

and

@IBAction func segueToCreate(sender: UIButton){
    tagId = String(sender.tag)//tagId needs to fetch the information
    parseJSON(tagId)
    performSegueWithIdentifier("segueToView", sender:self)
}
func parseJSON(tagID:String){

    Alamofire.request(.GET, "http://smarttags-001-site1.btempurl.com/SmartTagsRequests.aspx", parameters: ["AjaxFunc":"GetTagAttr","TagID":"\(tagID)"]).validate().responseJSON{ response in
        switch response.result{
        case .Success:
            if let value = response.result.value {

                let json = JSON(value)

                print("JSON: \(json)")
                self.TagName = json[0]["TagName"].stringValue
                NSLog("\(self.TagName)")
                self.ContentTitle = json[0]["ContentTitle"].stringValue
                NSLog("\(self.ContentTitle)")
            }
        case .Failure(let error):
            print(error)
        }enter code here 
    }
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    var ViewTest : ViewTwo = segue.destinationViewController as! ViewTwo
    var TagNameLabel = UILabel()
    TagNameLabel.frame = CGRectMake(74, 112, 182, 64)
    ViewTest.view.addSubview(TagNameLabel)
    TagNameLabel.text = TagName
    var ContentTitleLabel = UILabel()
    ContentTitleLabel.frame = CGRectMake(74, 180, 182, 64)
    ViewTest.view.addSubview(ContentTitleLabel)
    ContentTitleLabel.text = ContentTitle
}

}

Community · Accepted Answer · 2017-05-23 12:24:37Z

To follow up to MirekE's answer, here are some other steps you may want to consider:

Consider using Auto Layout in place of hard-coded frames, so your UI would adapt to different size classes.
Consider alternate approaches for showing an interactive list (of images) instead of programmatically adding buttons. For example, you could use a prototype (table view or collection view) cell. Cells are selectable and can take the place of a button. Other benefits include:
- A scrollable container, should you have more buttons than would fit on screen.
- A single segue (or selection) is handled by the storyboard prototype cell, instead of needing to make each programmatic "button" perform a segue (or action). Since you'd know which cell was selected, you'd no longer need a tag to figure that out.
Consider passing parameters to your destination view controller, instead of trying to instantiate and create controls in prepareForSegue. The destination's view is not loaded at that point.
Consider allowing the UI to feel more responsive, such as by performing the segue and showing placeholder details which you can then update once the network request completes. Otherwise, the user may have to wait for the network response before the segue occurs (which might make them think nothing happened and needlessly tap again, leading to an additional network request).

In general, Apple (or someone else) has already provided some way to do what you want, ideally leading to less code that you have to write, debug, test, and maintain to accomplish what you want your app to do.

MirekE · Accepted Answer · 2016-01-11 11:36:11Z

1

Most likely cause of the problem is your call to parseJson followed by prepareForSegue. parseJson is asynchronous and you don't get data back from your service before prepareForSegue is called. As a first step, move the prepareForSegue to the completion block of the parseJson.

answered Jan 11, 2016 at 11:36

MirekE

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