Closure (Blocks in Objective-C) Demo in swift 3.0.1

Block_Closure_Demo.swift

public class Custom {

    var success: ((Bool) -> String)?
    
    public func testBlock() {
        print(success!(true))
    }

}

let custom = Custom()
custom.success = { success in 
    print(success) 
    return "return string from block"
}

print("before block call")
custom.testBlock()
print("after block call")

Output.txt

before block call
true
return string from block
after block call