Scenario: Exploring the creation of a decorator to implement an interceptor for formatting output.
Issue at Hand: Encountering 'this' becoming undefined post application of the decorator.
// custom decorator
function UseAfter(this: any, fn: (...args: any) => any){
return (target: any, key: string, descriptor: PropertyDescriptor) => {
const originalMethod = descriptor.value
descriptor.value = (...innerArgs:any) => {
let result = originalMethod.apply(this, innerArgs)
return fn(result)
}
}
}
const formatData = (arg1: any) => {
return {
data: JSON.stringify(arg1)
}
}
class Example {
additionalMethod() {
console.log('performing instance method')
}
@UseAfter(formatData)
function1() {
console.log(this) // < --- now undefined
this.additionalMethod()
return 'success'
}
}
const exampleInstance = new Example()
exampleInstance.function1()