I was wondering if there was a way of dynamically taking an Instance of a class, so lets say I have a UIViewController called menu.
I could take menu's superclass which in this case would be UIViewController and create a subclass of it. I would then assign this new subclass to menu, I could also then dynamically override the methods as well.
So that when menu calls a method such as "ButtonClicked:" my code in the new Class I created fires followed by the original code when I call super :).
This all has to be done at runtime for security reasons.
Runtime subclassing is totally possible. Here's an introduction: http://www.mikeash.com/pyblog/friday-qa-2010-11-19-creating-classes-at-runtime-for-fun-and-profit.html
Although I'm curious... what "security" do you think you're getting by subclassing at runtime?
Related
I have a class that defines all styles on a UIVIew.
They are all predefined but I'm not sure when to fire this.
When I try to create an extension for this:
extension UIView
{
func willMoveToSuperview(newSuperview: UIView?)
{
self.stylize() // Another extension somewhere (not here my problem)
}
}
And I'm getting this error:
Method 'willMoveToSuperview' with Objective-C selector conflicts with
previews declaration with the same Objective-c selector
I have tried to override it, but didn't worked either.
Any ideas on how to be able to apply a same behaviour when all of my UIViews will become visible?
You can use Swizzling technic to customize UIView's function. Take a look at:
http://nshipster.com/method-swizzling/ (objective-c)
or
http://nshipster.com/swift-objc-runtime/ (swift)
Hope that helps.
Even though Swift's Extensions are similar to Categories from Objective-C, what you are trying to do is not allowed in Swift.
You cannot override existing functionality:
Extensions can add new functionality to a type, but they cannot override existing functionality.
Source: Swift Extensions - Apple Documentation
Depending on what it is that you are trying to style, you might want to take a look at UIAppearance, it will allow you to style default colors for the UINavigationBar, amongst other things. NSHipster has a good post about it: NSHipster - UIAppearance
You can create a subclass of UIView with the method .stylize().
Then each view you create, you inherit of you UIView subclass.
You'll be able to cal .stylize() on each UIViewSubclass. Simply write the style code inside the subclass and inherite.
Or
Use a category to add the method to the existing UIView class.
See : https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html
Outside of swizzling (not generally recommended), or subclassing as noted by David in his answer, there isn't really a way to override existing methods on a class and its subclasses.
One thing you might try is creating a base class for your view controller instead of all your views. In your view controller base class, you could override viewWillLayoutSubviews to recurse through the view hierarchy and call stylize on each view. This means you would be using the subclass approach in fewer places (just view controllers as opposed to all views).
Another thing you might consider if taking the subclassing approach with UIView is that if you are subclassing anyway, you can take advantage of things like #IBDesignable and #IBInspectable to better integrate those UIView subclasses with storyboards and live preview.
I wrote a Swift library which does exactly this, and it works well for the type of styling it seems you want to do: https://github.com/daniel-hall/Stylish
I would like to be able to interact with the UIControl I have made, and therefore want it in my ViewController.
What I tried
I subclassed UIControl (1).
Then I added a UIView to my View Controller and assigned it the new class (2).
But in Interface Builder I am not able to set my outlets to the buttons contained in the new class (1)?!
1:
2:
UIControl's documentation confirms that it is a subclass of UIView, and I should therefore be able to connect the outlets, right?
What am I missing here? :/
Off-course you can't add IBOutlet because buttons what you added to WeekdayControl are in UIViewController, you can't add Outlet to WeekdayControl, buttons only subviews of WeekdayControl, UIViewController is boss here, and you can add outlet only to UIViewController. (Sorry for my English)
Better create you buttons programatically in WeekdayControl.
Must read first:-
You cannot use the UIControl class directly to instantiate controls.
It instead defines the common interface and behavioral structure for
all its subclasses.
The main role of UIControl is to define an interface and base
implementation for preparing action messages and initially dispatching
them to their targets when certain events occur
So, you are doing wrong, if you really need to make a custom view or custom control then you can directly do it by creating a custom UIView and connecting the outlets directly with the view.
I think you missing the objective of subclassing a UIControl, it doesn't give rights to create outlets as it's a subclass of UIView,just read this lines what it is stated in the docs:-
Subclassing Notes
You may want to extend a UIControl subclass for either of two reasons:
To observe or modify the dispatch of action messages to targets for
particular events
To do this, override sendAction:to:forEvent:, evaluate the passed-in
selector, target object, or UIControlEvents bit mask, and proceed as
required.
To provide custom tracking behavior (for example, to change the
highlight appearance)
To do this, override one or all of the following methods:
beginTrackingWithTouch:withEvent:,
continueTrackingWithTouch:withEvent:, endTrackingWithTouch:withEvent:.
Recently I've been looking into RESideMenu. What really piqued my interest was his 'UIViewController+RESideMenu.h/m'. It appears to me that this is a way to subclass a UIViewController. It includes IBActions and methods in it that are accessible from anything that inherits from UIViewController.
All of my attempts to replicate this have failed. Is there a special way to go about it?
Usually that sort of classname is used to denote a category. Instead of subclassing it adds additional methods and properties to a class. For more information see here: CustomizingExistingClasses
I am learning to program the iphone and I wanted to do some drawing. I followed some example code and subclassed the viewcontroller and it worked fine. Now as I wanted to expand the program I came upon a design question that I could use a little help on.
I subclass myviewcontroller with mynewview. If I have any code in the myviewcontroller how do I call or reference it in mynewview and vice versa? I am not sure if I am asking this right but I am trying to understand the relationship between the class and subclass.
Objective-C objects benefit from inheritance. All classes are subclasses of NSObject, therefore you can call init on any object. If you created a custom class and gave it a method doSomethingAwesome, you are free to then implement doSomethingAwesome in any subclass of your custom class. However, declaring a method in a subclass does not add that method to the superclass. As an aside, I rarely find myself subclass sing my own custom classes. I believe that it is encouraged to maintain what is called a shallow object hierarchy. Usually I subclass the stock cocoa classes, customize to my needs and if I need custom methods in more than one subclass I will declare a category on the superclass rather than relying on inheritance to provide my custom behavior
The messaging system in Objective-C is dynamic. Every object includes a struct with information that the runtime use for introspection. Here the runtime will find a list of methods the object is able to respond. So, let's say you message an instance like this:
[mynewview someMethod];
The runtime will first check the object information to trying to find some method that will be able to respond the message. If nothing is found, then will query the super class, and so on. In fact, the runtime is much more complex, and will give any object more opportunities to respond (that's the dynamic part. For instance, mynewview might not have any method called someMethod and yet, might be able to satisfy the call, but that's something you might not want to worry right now).
From a child class you can call the superclass implementation of a given method with the keyboard super, so if mynewview is a subclass of myviewcontroller you can call myviewcontroller implementation from mynewview with:
[super someMethod];
If someMethod is both present in myviewcontroller and in mynewview, the runtime will automatically only call the child implementation, you have to call the parent implementation (if you have to) from the child implementation.
This should be easy - but I am scratching my head over it. Here's the problem:
I have a custom class that I import into my MainViewController.h file. The class contains a bunch of properties and a few methods.
I instantiate an object of this class in the ViewDidLoad section, and can run any of the methods or alter the properties on this object at will... they work fine as long as I stay within the ViewDidLoad section.
I created a button with which I wish to activate one of my custom class methods on this object, but the IBAction section seems out of scope, as it doesn't see the object created in ViewDidLoad at all.
Can someone point me in the right direction to enable these two areas to see eachother?
Thanks in advance!