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iOS Introduction to Table Views Static Table Views for Detail Interfaces Table View Headers

Rea Rahhal
PLUS
Rea Rahhal
Courses Plus Student 4,732 Points

Images don't display ...

Here is my Code:

ContactDetailController.swift;
import UIKit

class ContactDetailController: UITableViewController {

    var contact: Contact?////checking if we have a contact associated with the controller

    //outlets

    @IBOutlet weak var profileView: UIImageView!
    @IBOutlet weak var phoneNumberLabel: UILabel!
    @IBOutlet weak var emailLabel: UILabel!
    @IBOutlet weak var nameLabel: UILabel!
    @IBOutlet weak var StreetAddressLabel: UILabel!
    @IBOutlet weak var cityLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
configureViews()

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

//Configure View method to set up labels .Called when the view loads
    func configureViews(){
        //contact property is an optional so we unwrap it
        guard let contact = contact else {return}
        phoneNumberLabel.text = contact.phone
        emailLabel.text = contact.email
        StreetAddressLabel.text = contact.street
        cityLabel.text = contact.city
        profileView.image = contact.image
        nameLabel.text = "\(contact.firstName) \(contact.lastName)"//string interpolation to display first name and last name 

    }

and the ContctListController:

import UIKit

class ContactListController: UITableViewController {//view controller for the master view


    var contacts = ContactsSource.contacts

    override func viewDidLoad() {
        super.viewDidLoad()

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {//a section is a way to group data
        //asks data source to returna a number

        return 1// to specify that we have one section.We are goin to treat our data as a single long list of contacts so we will return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return contacts.count//we ant as many rows as contacts
    }
    //each row displays data in a cell 


    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {//this metod is called for each row and provides a value for the indexpath argument which indicates which section we are in and which row we are in
        let cell = tableView.dequeueReusableCell(withIdentifier: "ContactCell", for: indexPath)//ask the method to create a reusable cell from a prototype.
        let contact = contacts[indexPath.row]//display contacts at a particular index at a row that has the same index path
        cell.textLabel?.text = contact.firstName//assigning the contact first name to text label
        cell.imageView?.image = contact.image//displaying images
        cell.detailTextLabel?.text = contact.lastName
        return cell
    }


    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {


        //the code here is executed when we go from master to detail
        if segue.identifier == "showContact"{
            //the next step is to figure out which row was tapped
            if let indexPath = tableView.indexPathForSelectedRow{
                let contact = contacts[indexPath.row]
                //the dest vc is the nav controller the detail controller is embedded in

                guard let navigationController = segue.destination as?UINavigationController,let contactDetailController = navigationController.topViewController as? ContactDetailController

                    else{return}
                //getting a reference to the destination and casting it to the right type
            contactDetailController.contact = contact//assigniung this instance of the contact on the stored property on the contact detail controller
            }
        }
    }

Thanks in advance

I'm not advanced enough to do this. I will be someday, but I'm just on my first month of Swift/iOS coding yet.

Harold's response seems resonable though! If Apple encourages/tells you to load image files through the main que (what does this mean, "que"?) to load faster, then that is something that I would at least try.

Linus Karlsson,

A dispatch queue is a queue that you can put your code in to execution while there rest of your code continues on .. or it can be a queue of code you need to execute and you can say when your done. It probably seems weird because you may think - "well setting an image is such a simple task does it matter?" Yes:

this is getting advanced or intermediate but its important to know in iOS Dev or Engineering

DispatchQueue - Main - Async 
  • DispatchQueue is a structure that manages tasks or methods you you put in it.( with in the curly braces)...

(after dispatchQueue I use dot notation "." and the compiler tells me what "thread" I want to use...)

  • "Main" refers to the main thread of execution...

(There is the main thread and there is the background thread), in some states of America we have something called an "HOV lane" on the highway, or you can call it the fast lane where you are in less threat of being in slow traffic and you get to go faster then everyone else.

The "Main thread" of execution is like the" HOV lane" on a highway and all code execution will go much faster on this lane while lower priority tasks are done on the "default" "Background thread" (which are all the other lanes on the highway)

Lastly, in regards to threads and queues, you have the ability to create your own and manage what happens during after or before execution and thats where things are super advanced lol, but good to know about it may come up in an interview question to see if you know about it)

  • "async" is short for Asynchronous, which means other code written below the curly braces will continue while the code in side is still being executed... for example if Rea Rahhal does what I recommended then there will not be a hold up while the image is being set and loaded the code will skip onward and return his cell. (synchronous code would me the code has to finish its execution before moving forward)

At the end of it all the apple encourages us (really almost requires) to load UI elements, and Service calls (calling to servers) on the "main thread asynchronously"

  • Harold

1 Answer

Something you may want to try is putting your cell.imageView = contact.image on the main que... apple likes for you to do UI thing on the main thread so they appear faster you can try this by doing something like:

DispatchQueue.main.async {
        Cell.imageView.image = contact.image

}

Hope this helps buddy I was just walking on my lunch break,

Also set a break point on that line and make sure there is an image there at that time... you can do this by typing po contact.image in the console and see if it’s not nil if it’s nil the image is not successfully loading.