Is there a way to find out if interface's property is defined as read only? Say,
interface ITest {
readonly foo: number;
}
Now, is there some sort of reflection or trickery for TypeScript to get this information? E.g. something like:
let info = Reflect.get(ITest, 'foo');
if (info.isReadOnly()) { ... }
There is now: https://typescript-rtti.org/.
import { reflect } from 'typescript-rtti';
interface ITest {
readonly foo: number;
}
let iface = reflect<ITest>().as('interface').reflectedInterface;
let info = iface.getProperty('foo').type;
expect(info.isReadonly).to.be.true;
Disclaimer: I am the author
Since TypeScript interfaces do not exist at runtime, you cannot use reflection on them. To use reflection I created a class that implements the interface and reflected on the class. However, I was unable to tell if a property is readonly. Not sure if this is a lack of understanding on my part, or a defect. Here is what I tried:
Code
interface ITest {
readonly foo: number;
bar: number;
}
class TestImplementation implements ITest {
readonly foo: number = 1;
bar: number = 2;
}
function reflectOnTest() {
var testImplementation = new TestImplementation();
var properties: string[] = Object.getOwnPropertyNames(testImplementation);
var fooDescriptor = Object.getOwnPropertyDescriptor(testImplementation, properties[0]);
var barDescriptor = Object.getOwnPropertyDescriptor(testImplementation, properties[1]);
console.log("foo writable = " + fooDescriptor.writable);
console.log("bar writable = " + barDescriptor.writable);
}
Output is:
foo writable = true
bar writable = true
