I am programming vb.net. I would like to register everytime a property has been "set". But rather than create a Sub and call it from every property setter, I'd like it to be triggered automatically any time the setter is called. Is there any kind of "hookup" system I can use to achieve this?
There is an existing thread that explains how you can achieve this using the INotifyPropertyChanged Interface:
Implementing INotifyPropertyChangedEvent
Related
Is there way to add a property observer in Lua just like Swift does for WillSet and DidSet with properties?
For example, I have a object of display.newText and whenever I change it's text property. I need to do something other as well? Like
object.text = "Changed"
I know I can add a method like setText() or something but I'm looking for property observers in Lua language.
Thanks in advance.
Use a proxy table. This is explained in Pil, Chapter 13.
I'm just beginning with ObjC. I'm wondering how to find out when looking at code, written by me or from a template that comes when you use the wizard to create a new class, how you can tell if a method is overriding something.
In Java, you can mark a method with #Override, and then it's very easy to see if it's overriding something. That's not foolproof, because #Override is optional, but if I'm still unsure I can just type that in and see if it generates an error.
Is the only way to look up the source of the superclass, or in the case of a framework to read the documentation?
I don't know a way to see this immediately, but you could check if super responds
to the same selector. Example:
- (void)myMethod
{
// Temporarily add this line. If the compiler does NOT complain,
// "myMethod" overrides a method from some superclass.
[super myMethod];
// ...
}
You can use instancesRespondToSelector to see if your instance has an implementation of the method in its object hierarchy.
[MyClass instancesRespondToSelector:#selector(myMethod)];
or depending on what type of checking you need to do
[MyClassSuperClass instancesRespondToSelector:#selector(myMethod)];
I am new to Objective-C so sorry if this is inanely simple. I am trying to alter the PhoneGap Capture Feature to add some text on the audio and video capture screens that pop up when you call capture.captureAudio and capture.captureVideo.
I have found I can alter the Cordova source and change the loadView method of the CDVAudioRecorderViewController to add a text field and alter the appearance. Likewise I imagine I should be able to do the same with the CDVImagePicker class.
I know hacking the source of a library is a bad idea so I am wondering what are the other simple ways I could go about doing this?
Is there a sneaky simple way to substitute an inherited class in Objective-C? Perhaps by changing a factory (init) method somehow? If so, how do I set this up within my own codebase so that it will use my changes ahead of the original code?
If not does that mean I have to resort to creating a plugin that overrides CDVCapture find every method that mentions the classes I want to sub out and replace them with my new class that inherits form CDVAudioRecorderViewController just to override a single method on CDVAudioRecorderViewController?
ok so i have a bunch of methods in a class. How can i call those methods with out initiating it like:
Dim aa as new classname
aa.method
The reason i want to do so is so that i dont have to keep re initiating it to loose its variable data.
In php you can create a static method and then call that method without creating an instance of that class
how can we do this in vb?
The static equivalent in VB is Shared
I'm new to programming in Cocoa, so I'm still struggling to grasp some basic concepts.
What I want to do (as an example) is write an application with multiple NSTextFields. However, these NSTextFields need to be linked to separate classes. Additionally, each separate class needs to be able to get and set data from each other.
I tried to add methods to tackle this problem, to no avail. Let's say this is a method in the textbox's original class, and I want to call it from another class.
-(void)settextfield:(NSString*)stringy;
{
[TextField setStringValue:stringy];
}
Here's the calling code (we're calling this from another class, TestClass)...
-(IBAction)test:sender;
{
[BundleBrowseTextBox settextfield: #"Testy"];
}
Nothing happens. There's probably some obvious way to do this, but I haven't been able to unearth this via Google searches.
My mistake was that I was calling the class method instead of the instance... you can call the instance via IBOutlets and defining those outlets properly in Interface Builder.
You need to make sure the pointers you are using are not nil.
One odd/convenient thing about objC is that you can pass messages to nil and it won't crash.
If I'm right in assuming you're trying to set the text in an instance of BundleBrowseTextBox, you should call the settextfield: message on the instance name, rather than on the class name (if BundleBrowseTextBox IS the instance -- rather than the class -- you should really avoid capitalized instance names for clarity). i.e.:
-(IBAction)test:(id)sender;
{
// Assuming bbtBox is defined as an instance of BundleBrowseTextBox
[bbtBox settextfield: #"Testy"];
}
I believe you forgot your parameter type in your original post
this...
-(IBAction)test:sender;
{
[BundleBrowseTextBox settextfield: #"Testy"];
}
should be
-(IBAction)test:(id)sender;
{
[BundleBrowseTextBox settextfield: #"Testy"];
}
That aside if you understand the difference between class and instance as you say you do.
Then it would be nice if you would show us the rest of your implementation and interface.
The problem is probably not in the code snippets you showed us.