在通用接口中使用接口

Question

I use generics when using object literals to help simplify the process of interface building. So, for example, my base interface for all objects that use string as keys is

interface IStringTMap<T> { [s: string]: T; };

If I wanted to use this to enforce an object to be entirely made of functions I'd make a new interface

interface IStringFunctionMap extends IStringTMap<Function> { };

Occasionally, however, I want to use more complex objects. For example, let's say I wanted to build the following structure:

var obj = {
    "group_1" : {
        "func_1" : function() {},
        "func_2" : function() {}
    },
    "group_2" : {
        "func_1" : function() {},
        "func_2" : function() {}
    }
}

I can build this interface pretty easily from raw bits

interface IFunctionGroups { [s: string]: { [s: string]: Function } };

How would I go about making this more readable using my existing IStringTMap interface?

I've tried using my caveman logic, but just shoving one interface into another

interface IFunctionGroups extends IStringTMap<IStringFunctionMap>;

Gives me the following error:

An interface an only extend an identifier/qualified-name with optional type arguments.

Answer 1

Adding curly braces { } after your interface declaration corrects the problem:

interface IStringTMap<T> { [s: string]: T; }

interface IStringFunctionMap extends IStringTMap<Function> { }

interface IFunctionGroups extends IStringTMap<IStringFunctionMap> { }

var obj: IFunctionGroups = {
    "group_1" : {
        "func_1" : function() {},
        "func_2" : function() {}
    },
    "group_2" : {
        "func_1" : function() {},
        "func_2" : function() {}
    }
}

This compiles without errors or warnings to:

var obj = {
    "group_1": {
        "func_1": function () { },
        "func_2": function () { }
    },
    "group_2": {
        "func_1": function () { },
        "func_2": function () { }
    }
};