Difference between block (Objective C) and closure

问题:

In tutorials its written that functionally both are same even closure is more easier then block and its avoided the complexity of block and memory management, I've gone through many tutorials but except these I'm not getting the difference between swift's "closure" and Objective-C "block".

Can anybody explain this difference in deep. Any help would be appreciated.

回答1:

Excerpt From: Apple Inc. “Using Swift with Cocoa and Objective-C.” iBooks:

“Swift closures and Objective-C blocks are compatible, so you can pass Swift closures to Objective-C methods that expect blocks. Swift closures and functions have the same type, so you can even pass the name of a Swift function.

Closures have similar capture semantics as blocks but differ in one key way: Variables are mutable rather than copied. In other words, the behavior of __block in Objective-C is the default behavior for variables in Swift.”

回答2:

Slight differences. One was mentioned; variables are captured as variables, not as values. Which can be either useful or a trap. Importantly you can define a capture list in a Swift closure, so if you include self.property in the capture list, then the value of that property is captured, and not self. That also simplifies capturing weak variables.

回答3:

To show an actual code example of the differences:

This does compile:

let x : @convention(swift) (inout Int) -> ()

This does not:

let y : @convention(block) (inout Int) -> ()

with the error (inout Int) -> () is not representable in Objective-C