如何将OR运算符与可选绑定一起使用？

Question

I have a piece of code that I would like to execute if a variable can be casted as one of two types.

if let myOptional = variableToCast as! firstTypeToTryToCastAs || 
   let myOptional = variableToCast as! secondTypeToTryToCastAs {
        //Execute some code
}

However, Swift (as of version 2.0) apparently does not allow this. I'm looking for a way to do this without having to create two separate if blocks.

My code only uses the super type, therefore the code dealing with both types are the same. However, I can't cast it to the super type because I don't want to code to execute if variableToCast is one of the many other possible types that are also derived from the same super type.

Answer 1

Based on your comment:

My code only uses the super type, therefore the code dealing with both types are the same. However, I can't cast it to the super type because I don't want to code to execute if variableToCast is one of the many other possible types that are also derived from the same super type.

In your optional binding if let cast to the super type and then limit it to the classes you are interested in with a where clause:

class SuperType {

}

class firstTypeToTryToCastAs: SuperType {

}

class secondTypeToTryToCastAs: SuperType {

}

class thirdTypeToTryToCastAs: SuperType {

}

var variableToCast: AnyObject = firstTypeToTryToCastAs()

if let myOptional = variableToCast as? SuperType where myOptional is firstTypeToTryToCastAs || myOptional is secondTypeToTryToCastAs {
    print("this works")
} else {
    print("not the type we are looking for")
}

Answer 2

I'm looking for a way to do this without having to create two separate if blocks

Why?

You can't use the same code in the if block anyway because myOptional will be of a different type. I would go with

if let myOptional = variableToCast as! firstTypeToTryToCastAs
{
    // code dealing with a firstTypeToTryToCastAs
}
else if let myOptional = variableToCast as! secondTypeToTryToCastAs
{
    // code dealing with a secondTypeToTryToCastAs
}

On the other hand if your two types have a common super type, cast it to that super type.

Answer 3

To add onto JeremyP's answer, if you don't actually care what the value of myOptional is, but just want to execute some code if it is one of those two types, you could do this instead

if variableToCast is firstTypeToTryToCastAs || variableToCast is secondTypeToTryToCastAs {
    //Code for both cases
}