Completion Blocks Syntax in Swift

Question

Slowly getting into Swift but still struggling with the completion blocks. How would the following code look like in Swift?

[self.eventStore requestAccessToEntityType:type completion:^(BOOL granted, NSError *error) {
    dispatch_async(dispatch_get_main_queue(), ^{
        [self alertViewWithDataClass:((type == EKEntityTypeEvent) ? Calendars : Reminders) status:(granted) ? NSLocalizedString(@"GRANTED", @"") : NSLocalizedString(@"DENIED", @"")];            
    });
}];

Answer 1

self.eventStore.requestAccessToEntityType(type) {
    (granted: Bool, err: NSError!) in
    dispatch_async(dispatch_get_main_queue()) {
        ...
    }
}

for an example of working code, I was experimenting with this exact API in swift :)

Answer 2

Your Objective-C 'completion blocks' in Swift (now called 'closures' in this context) will contain all of the same information:

1. parameter labels and types (at the start of the block in parentheses)
2. return type (preceded by '->')
3. the keyword 'in' separating the signature from the code

Note that the signature of the method specifies the type for the parameters, so all you really need to do there is supply names for them :) (type inference FTW!) Additionally, your block returns 'Void' so we don't need to include the return type here, either.

That would give us:

self.eventStore.requestAccessToEntityType(type) { (granted, err) in
    dispatch_async(dispatch_get_main_queue()) {
        ...other stuff...
    }
}