Swift：比较泛型类中的泛型类型

Question

I'm creating a Matrix class in swift, which I want it to be Generic, so I can use it Like this:

let matrix: Matrix<Character>; // Or any other type

I created my class like this:

class Matrix<Template>: NSObject {}

I am crating a function that Apply Gravity to matrix that takes an emptyKey of type Template, and drags every element not equal to emptyKey to the bottom of the matrix

// For example emptyKey is "_" and Template is String.

1 _ 2               1 _ _
3 4 5   == To ==>   3 _ 2
6 _ _               6 4 5

The problem is: when I am trying to compare the value in matrix at a specific location which of type Template with the emptyKey which also of type Template , it fails to compile and gave me the error:

Binary operator '==' cannot be applied to two 'Template?' operands

I am using xcode 7.3.1 with Swift 2.2

Answer 1

You need to constrain Template to Equatable.

class Matrix<Template:Equatable> ...

(Also I would advise that you avoid Optionals. I don't know where you're using them, but your error message suggests that you are, and they are going to get in your way.)