CODEWITHSUNDEEP
typescripttypes
option 12
option 12

Reputation: 23

Define Function Type, Function Interface in Typescript

Is it possible to define a function interface in typescript?

for instance, when we have things such as 

meth (a : {b: B, c: C}) : {b: B, c: C} {...}

we can write

interface A {
    b : B;
    c : C;
}
meth (a : A) : A {...}

however, when we have something like 

meth (a : (b: B) => C) : (b: B) => C {...}

can we do something similar, like define a function type so that we can write 

meth (a : A) : A {...}

again?

Upvotes: 2

Views: 132

Answers (1)

Titian Cernicova-Dragomir
Titian Cernicova-Dragomir

Reputation: 250366

Interfaces support call signatures. Actually the syntax you use can be seen a shorthand for the more verbose full syntax: 

interface A 
{
    (b: B) : C
}
function meth (a : A) : A { return a; }

The interface syntax also has the advantage of supporting multiple overloads for the function : 

interface A {
    (b: B): D
    (d: D, b: B): C
}
function meth(a: A) : void
{
    a(new B()); // Call overload with one argument
    a(new D(), new B()); // Call overload with two arguments 
}

meth((b: B | D, d?: D|B) => new D());

Upvotes: 1

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