CODEWITHSUNDEEP
gointerface
kovac
kovac

Reputation: 5389

Declaring interfaces in GoLang with array symbol

I have seen interfaces defined like:

type MyInterface interface{
   Method()
}

and

type MyInterface []interface{
   Method()
}

What is the difference in these two definitions?

Upvotes: 2

Views: 252

Answers (3)

Joao Henrique
Joao Henrique

Reputation: 587

The first one is an interface declaration with a method method() declared in it.

type MyInterface interface{
   Method()
}

The second is that a variable with type []interface{} is not an interface! It is a slice whose element type happens to be interface{}

type MyInterface []interface{
   Method()
}

Plus, a variable with type []interface{} has a specific memory layout, known at compile time.

Upvotes: 0

dom
dom

Reputation: 444

Basically when you create

type Iface interface {
    Age() uint
    Name() string
}

type SliceIface []interface {
    Age() uint
    Name() string
}

// then SliceIface and []Iface has the same behaviour

so you could say

type SliceIface []Iface

Have a look at following code

https://play.golang.org/p/DaujSDZ8p-N

Upvotes: 0

leaf bebop
leaf bebop

Reputation: 8232

The first is defining an interface with a method of Method(), while the second is defining the a slice of interface. The statement utilizes the form of type literal and can be interepted as:

type MyInterface [](interface{
   Method()
})

Where interface{...} here is a type literal. Which has the same effect of

type I = interface{
   Method()
}
type MyInterface []I

See more on type literal: https://golang.org/ref/spec#Types

Note: MyInterface would be a very bad name in the second one.

Upvotes: 1

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