Equivalent objective C from Swift

Baart 0
Viewed 52

I'm following a documentation on braintree for IOS.

It recommends to implement a method like this (in swift):

func onLookupComplete(_ request: BTThreeDSecureRequest, result: BTThreeDSecureLookup, next: @escaping () -> Void) {
  // Optionally inspect the lookup result and prepare UI if a challenge is required
  next()
}

My target code is some objective C for react native module where function are defined like this :

RCT_EXPORT_METHOD(getAddressLine1: (NSString *) address 
  callback: (RCTResponseSenderBlock) callback)
{ ... }

What would be the equivalent of the swift implementation for the objective C module (especially the "next: @escaping" part) ?

Note: here is the braintree doc

Thank you

objective-c swift ios react-native
1 Answers

next: @escaping () -> Void

So () -> Void, that's called a closure, and in Objective-C, it's called a Block.

@escaping means that the method will "end" before the closure is called. In other words, if you have func myMethod(escaped: @escaping () -> Void) -> Bool, and if you write

let methodOutput = myMethod(escaped: { 
    print("here closure has been called")
}
print(methodOutput)

print(methodOutput) has strong chances (but not necessarily) to be printed before print("here closure has been called"). Usually because it's async.

Now, here's a sample from a UIView method to know how to translate them:

In Swift:

class func animate(
    withDuration duration: TimeInterval,
    animations: @escaping () -> Void
)

In Objective-C:

+ (void)animateWithDuration:(NSTimeInterval)duration 
                 animations:(void (^)(void))animations;

Now, I've said that it's not mandatory for it to be asynchronously called, because we could image this scenario in pseudo code:

func myMethod(escaped:  @escaping () -> Void)) {
    if canBeDone == false { //In Swift, a guard is better
        escaped()
    } else {
        doLongAsyncProcess(onDidFinished: { escaped() })
    }
}

If canBeDone is false, the closure will be called directly (synchrone), but if not, it will be called later (asynchrone).

Larme0
Related