Use Objective-C blocks in swift

Question

I have a third party Objective-C library in my swift project, in one of the .h files, it has a typedef:

typedef void (^YDBlutoothToolContectedList) (NSArray *);

and inside the class, it has a property:

@property (nonatomic, copy) YDBlutoothToolContectedList blutoothToolContectedList;

(please ignore its spelling)

When I try to use this property in my swift class, I use

bt.blutoothToolContectedList = {(_ tempArray: [Any]) -> Void in
    self.devices = tempArray
    self.tableView.reloadData()
}

and I got the error says:

Cannot assign value of type '([Any]) -> Void' to type 'YDBlutoothToolContectedList!'

I know the above Objective-C code in swift would be:

typealias YDBlutoothToolContectedList = () -> Void

but I can't re-write that Objective-C file and swift can't cast the closure type, is there a possible way to solve this problem?

Martin R · Accepted Answer · 2016-11-07 08:40:00Z

13

typedef void (^YDBlutoothToolContectedList) (NSArray *);

is mapped to Swift as

public typealias YDBlutoothToolContectedList = ([Any]?) -> Swift.Void

because the closure parameter can be nil. (You can verify that by selecting the .h-file and then choosing Navigate->Jump to Generated Interface in the Xcode menu.)

Therefore the correct assignment would be

bt.blutoothToolContectedList = {(_ tempArray: [Any]?) -> Void in
    // ...
}

or simply let the compiler infer the parameter type:

bt.blutoothToolContectedList = { tmpArray in
    // ...
}

If you could add a nullability annotation to the Objective-C definition:

typedef void (^YDBlutoothToolContectedList) (NSArray  * _Nonnull );

then it would be mapped to Swift as

public typealias YDBlutoothToolContectedList = ([Any]) -> Swift.Void

edited Nov 7, 2016 at 8:40

answered Nov 7, 2016 at 8:33

Martin R

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2 Comments

Compound07 Over a year ago

Thanks! I don't have much OC experience, so sometimes it's difficult for me to read some of the OC source codes and try to convert them into Swift.

Martin R Over a year ago

@SensEyeNULL: You are welcome! Does this answer your question? Please let me know if you need more information.

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