Interfaces in AngelScript

import math from "math";
import string from "string";

interface geometry {
    float area();
    float perim();
}

class rect {
    float width;
    float height;

    rect(float w, float h) {
        width = w;
        height = h;
    }

    float area() {
        return width * height;
    }

    float perim() {
        return 2*width + 2*height;
    }
}

class circle {
    float radius;

    circle(float r) {
        radius = r;
    }

    float area() {
        return math::pi() * radius * radius;
    }

    float perim() {
        return 2 * math::pi() * radius;
    }
}

void measure(geometry@ g) {
    print(g);
    print(g.area());
    print(g.perim());
}

void main() {
    rect r(3, 4);
    circle c(5);

    measure(r);
    measure(c);
}

Interfaces are named collections of method signatures. In AngelScript, we can define interfaces similarly to classes, but without implementation.

Here’s a basic interface for geometric shapes:

interface geometry {
    float area();
    float perim();
}

For our example, we’ll implement this interface on rect and circle types:

class rect {
    float width;
    float height;
    // ... implementation ...
}

class circle {
    float radius;
    // ... implementation ...
}

To implement an interface in AngelScript, we just need to implement all the methods in the interface. Here we implement geometry on rect:

class rect {
    // ... other members ...

    float area() {
        return width * height;
    }

    float perim() {
        return 2*width + 2*height;
    }
}

The implementation for circle:

class circle {
    // ... other members ...

    float area() {
        return math::pi() * radius * radius;
    }

    float perim() {
        return 2 * math::pi() * radius;
    }
}

If a variable has an interface type, then we can call methods that are in the named interface. Here’s a generic measure function taking advantage of this to work on any geometry:

void measure(geometry@ g) {
    print(g);
    print(g.area());
    print(g.perim());
}

The circle and rect classes both implement the geometry interface so we can use instances of these classes as arguments to measure:

void main() {
    rect r(3, 4);
    circle c(5);

    measure(r);
    measure(c);
}

When you run this program, it will output the area and perimeter of both the rectangle and the circle.

Note that AngelScript uses @ for handle (reference) parameters, which is similar to how interfaces are typically used in other languages.

Methods in AngelScript

Enums in AngelScript

Learn X By Example

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Interfaces in AngelScript