TypeScript Version: 2.4.1
Code
I have a 3rd party component that requires occasionally to think it is receiving an object like an array but with keys as the string indexes of the window of the grid it represents and the values being the row objects. (IE: if I want to pass the grid rows 5-9 of my data source I need to send it
{ "5":{"id":5}, "6":{"id":6}, "7":{"id":7}, "8":{"id":8}, "9":{"id":9} }I had a proxy handler that allowed me to pass in an array and a start index (so a 5 element array, and a start index of 5 in this example) and the proxy would be seen as this object by the grid.
But the code no longer compiles.
export class DataProxyHandler implements ProxyHandler<{}> {
private static readonly descriptor: PropertyDescriptor = { configurable: true, enumerable: true, writable: false };
constructor(public readonly startIndex: number, public readonly data: any[]) {
}
enumerate(target: {}) {
return this.ownKeys(target);
}
get(target: {}, property: PropertyKey) {
if (typeof property !== 'string') {
return undefined;
}
const { startIndex, data } = this, index = parseInt(property);
return isNaN(index) ? undefined : data[index - startIndex];
}
getOwnPropertyDescriptor(target: {}, p: PropertyKey) {
return typeof p !== 'string' || !this.has(target, p) ? undefined : DataProxyHandler.descriptor;
}
getPrototypeOf(target: {}) {
return Reflect.getPrototypeOf(target);
}
has(target: {}, property: PropertyKey) {
if (typeof property !== 'string') {
return false;
}
const { startIndex, data } = this, index = parseInt(property);
return !isNaN(index) && index >= startIndex && index < startIndex + data.length;
}
isExtensible(target: {}) {
return false;
}
ownKeys(target: {}) {
const { startIndex, data } = this;
return data.map((item, index) => (startIndex + index).toString());
}
set(target: {}, property: PropertyKey, value: any): boolean {
throw new Error('Can not set');
}
}Expected behavior:
Code would compile
Actual behavior:
Types of property 'getOwnPropertyDescriptor' are incompatible.
Type '(target: {}, p: PropertyKey) => PropertyDescriptor | undefined' is not assignable to type '((target: {}, p: PropertyKey) => PropertyDescriptor) | undefined'.
Type '(target: {}, p: PropertyKey) => PropertyDescriptor | undefined' is not assignable to type '(target: {}, p: PropertyKey) => PropertyDescriptor'.
Type 'PropertyDescriptor | undefined' is not assignable to type 'PropertyDescriptor'.
Type 'undefined' is not assignable to type 'PropertyDescriptor'.
I can get it to compile by specifying the return type of the method getOwnPropertyDescriptor as any.
getOwnPropertyDescriptor(target: {}, p: PropertyKey): any {
return typeof p !== 'string' || !this.has(target, p) ? undefined : DataProxyHandler.descriptor;
}
TypeScript Version: 2.4.1
Code
I have a 3rd party component that requires occasionally to think it is receiving an object like an array but with keys as the string indexes of the window of the grid it represents and the values being the row objects. (IE: if I want to pass the grid rows 5-9 of my data source I need to send it
{ "5":{"id":5}, "6":{"id":6}, "7":{"id":7}, "8":{"id":8}, "9":{"id":9} }I had a proxy handler that allowed me to pass in an array and a start index (so a 5 element array, and a start index of 5 in this example) and the proxy would be seen as this object by the grid.
But the code no longer compiles.
Expected behavior:
Code would compile
Actual behavior:
Types of property 'getOwnPropertyDescriptor' are incompatible.
Type '(target: {}, p: PropertyKey) => PropertyDescriptor | undefined' is not assignable to type '((target: {}, p: PropertyKey) => PropertyDescriptor) | undefined'.
Type '(target: {}, p: PropertyKey) => PropertyDescriptor | undefined' is not assignable to type '(target: {}, p: PropertyKey) => PropertyDescriptor'.
Type 'PropertyDescriptor | undefined' is not assignable to type 'PropertyDescriptor'.
Type 'undefined' is not assignable to type 'PropertyDescriptor'.
I can get it to compile by specifying the return type of the method getOwnPropertyDescriptor as any.