Abstract type: Difference between revisions
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Sub Method_Must_Be_Implemented()
End Interface</lang>
=={{header|Vlang}}==
{{trans|go}}
Vlangs ''interface type'' is an abstract type. It defines a set of methods that a ''concrete type'' must have to satisfy it.
A variable of an interface type can hold a value of any type that implements the methods that are specified in the interface. You don't need to explicitly "declare" that the type "implements" the interface or anything like that -- the compatibility is purely structural based on the methods.
In the following example, the Dog and Cat types both satisfy the Beast interface because they each have the specified methods. The ''bprint'' function can print details for any Beast.
<lang vlang>interface Beast {
kind() string
name() string
cry() string
}
struct Dog {
kind string
name string
}
fn (d Dog) kind() string { return d.kind }
fn (d Dog) name() string { return d.name }
fn (d Dog) cry() string { return "Woof" }
struct Cat {
kind string
name string
}
fn (c Cat) kind() string { return c.kind }
fn (c Cat) name() string { return c.name }
fn (c Cat) cry() string { return "Meow" }
fn bprint(b Beast) {
println("${b.name()}, who's a ${b.kind()}, cries: ${b.cry()}.")
}
fn main() {
d := Dog{"labrador", "Max"}
c := Cat{"siamese", "Sammy"}
bprint(d)
bprint(c)
}</lang>
{{out}}
<pre>
Max, who's a labrador, cries: "Woof".
Sammy, who's a siamese, cries: "Meow".
</pre>
=={{header|Wren}}==
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