This question already has an answer here:
Closed 10 years ago.
Possible Duplicate:
Asterisk in parenthesis in Objective-C… What does it mean?
does anyone can find some resource or detail explanation about following code
-(void) add:(Cal *)c;
I am very new to obj-c.what does asterisk means in that code?
Thanks.
It means that the argument for the method is a pointer to an instance of a "Cal" object.
Related
This question already has an answer here:
Use objective-c method in swift seems crossing keyword of swift language
(1 answer)
Closed 6 years ago.
I am trying to use a method from Objective-C in Swift 3, but Swift 3 is translating the signature to something invalid for the compiler.
- (void)doWhenReady:(void(^)(void))block onDone:(ErrorCallback)callback;
Gets translated to
do(whenReady: ()->(), onDone: ErrorCallback)
Where do becomes the keyword do and invalid syntax for the method. What solutions do I have to fix this without refactoring the Objective-C code?
In the Swift expression do(whenReady..., write do with backtick characters around it.
This question already has answers here:
What does a type name in parentheses before a variable mean?
(3 answers)
Closed 8 years ago.
I'm learning objective-C and I was looking at some sample code from:
https://developer.apple.com/library/ios/samplecode/UsingPhotosFramework/Listings/SamplePhotosApp_AAPLAssetGridViewController_m.html#//apple_ref/doc/uid/TP40014575-SamplePhotosApp_AAPLAssetGridViewController_m-DontLinkElementID_8
I'm confused about this line of code here:
CGSize cellSize = ((UICollectionViewFlowLayout *)self.collectionViewLayout).itemSize;
I understand that it's trying to get the itemSize property and store it into cellSize, but I have no idea what ((UICollectionViewFlowLayout *)self.collectionViewLayout) is all about. Can someone break it down for me? Is there another way to write this line of code?
What it means is:
Cast self.collectionViewLayout to be of UICollectionViewFlowLayout type. Then of self.collectionViewLayout get the itemSize property. Finally, save everything is a property of type CGSize.
I believe is a elegant and concise way of writing it.
This question already has answers here:
Caret in objective C
(3 answers)
Closed 9 years ago.
There is a piece of code like
typedef void (^SignIn) (NSString *email, NSString *password);
What does the ^ mean before SignIn? Is this Objective-C specific usage?
It's the syntax for blocks.
That typedef declares SignIn to mean a block which takes two NSString* arguments and returns void (i.e. nothing).
It is a block.
For a guide to understanding blocks, see this tutorial
Unless, you already know what a block is, and you just didn't know what the caret was for.
This question already has answers here:
How can I call a method in Objective-C?
(8 answers)
Closed 9 years ago.
I am just starting out in ios and am trying to make user defined functions...
my code:
-(void) testFunction{
//has self. calls
}
-(IBAction)button:(id)sender {
testFunction();
}
I get the warning: Implicit declaration of function is invalid in C99
What am I doing wrong? Or what do I have to add to my code?
In Objective-C you cant write testFunction(). You send 'messages' and you can do this via
[self testFunction]
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
NSLog 10b meaning?
I am new to objc and iOS development. And, I have a question about NSLog. As we know, NSLog will log message like this:
2011-07-16 23:19:35.467 HelloWorld[11166:7c37] say hello to iOS.
Obviously the format is date time ProjectName, but what does the [11166:7c37] part mean?
Its a process / thread ID I believe.