I was wondering if there's a way to mark a class as "needing disposal" in Dart.
What I mean to do is replicate the linter warning that gets shown, for example, when I create a StreamController and not dispose it somewhere in my code, the close_sinks warning is shown.
This does not happen for other classes like AnimationController or ValueNotifier.
What does make a class raise this kind of warning? How can I replicate that for my own needs? Can I at all?
Thanks in advance!
At the moment there is no way, but you can follow the issue progress here: https://github.com/dart-lang/linter/issues/697
Related
I came from Android background and I'm new to Swift.
I want to know how to use common functions in ViewControllers with DRY principles.
I need all of my ViewControllers to call following functions from one place:
isNetworkAvailable() //check app has internet return boolean
getLoggedinUser() //return logged in user object which I set before
showAlert(message:String) //display a popup
startLoader() // display a loader
stopLoader() // stop loader
As you can see these methods are global and I need to reuse them many times. So I don't want to copy paste the same code over and over again.
In Android I simply make one BaseActivity and put all those methods in it. Later I will extend the BaseActivity into SubActivities and inherit those common methods.
I'm not sure how to do this in "IOS Swift" as all the ViewControllers are attached to StoryBoard.
Can you please tell me what is the best way to achieve this? How does professional Swift developers handle situations like this?
(Please note - I don't want to delete story board and manually create UI elements.)
Thanks in Advance!
Create a CommonFunctions named public class (just a suggestion you can name it any class name which you want) extend it from NSObject and import UIKit Module in it because I think you also want to perform UI Operations in it like startLoader() & stopLoader() then you can write static global methods which you are mentioned in your question.
You can call then using CommonFunctions.methodName().
Or if you don't want to make static functions then create object of CommonFunctions class wherever you want to access those global methods and call the method which you want.
In Xamarin documentation for Foundation.NSObject, in Lifecycle section, it says:
C# NSObjects are also created on demand when you invoke a method or a property that returns an NSObject. At this point, the runtime will look into an object cache and determine whether a given Objective-C NSObject has already been surfaced to the managed world or not. If the object has been surfaced, the existing object will be returned, otherwise a constructor that takes an IntPtr as a parameter is invoked to construct the object.
Is there a way to do the above from my code? In other words, given an IntPtr handle, can I get a C# NSObject if it already exists or let Xamarin create a new one if it doesn't?
The reason I want to do the above is that I want to keep the IntPtr handle of a C# NSObject and then Dispose() it. Later in the code, I want to get the NSObject back from that IntPtr.
The reason I want to do the above is that I've read enough documentation, blogs and SO questions about the interaction between the C# garbage collector and the native refcounted objects in Xamarin.iOS that I decided to Dispose() everything as soon as possible. So in all methods, I use using whenever I get an NSObject argument. For example:
[Foundation.Action("buttonPressed:")]
public void RatingButtonTapped(UIButton button) {
using (button) {
Console.WriteLine("Hello world");
}
}
So if I had kept a reference to the UIButton earlier during initialization, it will be disposed when this action is run. So instead, I plan to keep the IntPtr handle instead and re-get the UIButton when I need it later.
You can use this method to get the managed object for a handle:
ObjCRuntime.Runtime.GetNSObject (handle);
But have in mind that if the native object has been freed, you will crash.
If you don't want to crash, you need to retain the native handle, and then release it when you don't need it anymore.
If you add logic to retain+release the native handle, then you can just as well keep the managed object around, and only call Dispose when you determine you don't need the object anymore.
Curiously you link to the XY problem, and you're falling into that exact trap: your actual problem is that you have memory leaks (I assume, but you didn't explain), and you're asking about your attempted solution (dispose everything).
But that's the wrong solution to the problem. You will run into a world of pain with this solution (you've already found one, and if you go ahead with keeping handles around you'll end up in a much worse place: how to solve crashes instead of how to solve memory leaks).
The correct solution is:
Diagnose (and profile) to understand what's really happening (with the memory leaks).
Only dispose objects that you know are no longer needed (and that the GC couldn't already determine isn't needed). You want to dispose as little as possible (it makes your code easier to maintain), and you need to do step 1 first in order to know those objects.
I am using Collapseclick library for Acccordian functionality. I am facing issue if trying to call -(UIView *)viewForCollapseClickContentViewAtIndex:(int)index; method and replacing switch case with for loop. I am new to objectiveC. Please help me out!
Honestly it is hard to recommend you a solution without knowing how the library code is set up, but you can try subclassing whatever class implements that method. If that method is on a certain class, make another class that is a subclass of that class and override that method. Expose whatever variables you need to, if they are not already exposed in that library.
See this documentation for more instruction on subclassing:
https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html
I have been stumped on this for awhile. I have asked multiple developers I know and they think I have forgotten to "#import the .h file". But I know I have, I have tested the class in more than one file in my project. It only works in the "VNDecalLevelListViewController.h" ( which I will post its implementation if a picture). When I try and call my "initForNewDecal" method for my "VNDecalCreatorViewController.h" class in my "VNAdminViewController.h" class I received the error that this method has not been declared in "VNDecalCreatorViewController.h". But when I call it in my "VNDecalLevelListViewController.h" class it works.
I am able to allocate and use "init" to create the object and it loads with a work around I made. But I am new to programming and I can tell there is definitely a better solution.
As you will soon see as i got to allocate the VNDecalCreatorViewController in the " VNAdminViewController" the option to initialize VNDecalCreatorViewController with the proper initializer "initForNewDecal" isn't even a option.
Anyone know why this is happening ? I want to write the code right I am trying to figure out why my header file is only being read in one class.
I guess this is because you mutually imported between the two class Creator and Level. I mean you may have #include "VNDecalCreatorViewController.h" in VNDecalLevelListViewController.h and vice versa. The solution is to use #class to forward declare any classes you may need to reference instead of #import'ing the header.
Make sure that the method is declared in the header file and implemented in the .m file.
Using Doxygen i have documented the methods declared by me and could generate documentation.
but i am looking for documenting the view life cycle methods and even delegate methods.
Can any one help me in achieving my requirement. All i am looking for is the equivalent documentation in doxygen as { #inherited } in javaDoc
Take a look at this It will give you an idea for what syntax to use for objective-c.
Edit: For docs on the View lifecycle, you would need to decide if you are doing anything outside of the ordinary that justifies needing comments(are you doing more than just updating data on viewwillappear).If you are can the code in those sections be broken out into another method (and then commented on the same as a normal method which would be my suggestion).
Hope this helps.