Скачать или смотреть Instantiating a View Controller in Xcode with Custom Variables: A Simple Guide to UIViewControllers

Discover how to properly instantiate a `UIViewController` in Xcode and modify its properties without confusion. Learn about using custom variables instead of static ones.
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This video is based on the question https://stackoverflow.com/q/75059943/ asked by the user 'mtacki' ( https://stackoverflow.com/u/8362483/ ) and on the answer https://stackoverflow.com/a/75060432/ provided by the user 'DonMag' ( https://stackoverflow.com/u/6257435/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Instantiating a View Controller in Xcode with Custom Variables

When developing iOS applications using Xcode, you might find yourself needing to instantiate a view controller from a storyboard and modify its properties. This often raises questions around how to manage variables effectively between different view controllers. In this post, we will solve a common issue where developers mistakenly attempt to change a static variable of a view controller, leading to unexpected behavior. Let’s dive in!

The Problem

You have a view controller called vc1 where you want to update its title from another view controller, say ViewController. However, upon trying to modify a static variable directly, your changes don't reflect in the interface. You may find yourself asking:

Why can't I update a static variable after instantiation, and what should I do instead?

Here’s how the original structure looks:

Example Code of vc1

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Example Code of ViewController

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Identification of the Issue

In the code above, when you try to set vc.title = "bla", you are actually trying to overwrite the static variable title, which won't work as expected. Static variables belong to the class itself rather than any instance of the class. Therefore, any change made to the static variable doesn’t affect the instance-specific behavior.

The Solution

Instead of using a static variable, the preferred approach is to utilize an instance variable. Below are the steps to properly implement this change:

1. Change Static Variable to Instance Variable

You need to declare an instance variable in your view controller (vc1) to hold values unique to each instance:

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2. Update Your Root ViewController Code

In your ViewController, you will change the instance variable before presenting the new view controller:

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3. Running the Application

Now, when you run the application and tap the button, the new view controller will present, and the title label should reflect the text "bla" as intended!

Conclusion

By using instance variables over static properties, you can easily pass data and manage behavior between different view controllers in your app efficiently. This adjustment allows you the freedom to customize each instance without facing the complications associated with static variables.

When building your iOS applications, remember to think in terms of instances rather than static classes, ensuring your variables retain the behaviors and values you need. Happy coding!