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.
Related
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 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.
This question already has answers here:
Semicolon after the method name in Objective-C implementation file
(6 answers)
Closed 9 years ago.
I'm trying to figure out why gcc is OK with the following:
- (void) methodname: (id) sender;
{
// do stuff
}
Notice what's wrong here: There is a semicolon that should not be there.
I'm also finding that execution of the method is having bizarre results.
Anybody know what effect the semicolon is supposed to have or not have here?
Thanks.
The semi-colon is optional in the context of the #implementation. Some teams standardize on requiring it, some don't.
In general ; makes it a function prototype. But the compiler must be smart enough to ignore it in this case. I don't think it's the ; that's causing your odd issues but I'm not sure.