如何在类中将数字转换为枚举打字稿

Question

I have this class

export class InstructorEvent {
EventID: number;
EvaluationMethod: number;

get EvalMethodEnum(): EvaluationMethodEnum {
    return 
EvaluationMethodEnum[EvaluationMethodEnum[this.EvaluationMethod]];
     }

 }


export enum EvaluationMethodEnum {
    None = -1,
    Test = 0,
    AssessmentForm = 1,
    PassFailDecision = 2,
    ParticipantSelfDeclaration = 3,
    ActivityAccess = 4,
    GradeDecision = 5,
    Courseware = 6,
    SCORM = 7,
    Attendance = 8,
    ObjectiveEvaluationManualGrade = 9,
    ObjectiveEvaluationPassFail = 10,
    ObjectiveEvaluationNone = 11,
    ObjectiveEvaluationCustom = 12,
    ObjectiveEvaluationAutoGrade = 14
}

Now i am getting all the data from the server as follow

this._service.getInstructorEvaluations(this.InstructorID).then(result => {
  if (result) {
    console.log(result);
    this.Events = result;

this.Events.forEach(element => {
  console.log(element.EvalMethodEnum);
    });
  }
});

The 'Events' property contains list of InstructorEvent objects...

But it returns 'undefined', any idea what am i doing wrong?

Answer 1

When you set this.Events = result , the items in this.Events aren't recognized as InstructorEvents, and if you simply cast them, the properties inside don't get initialized. You need to define a constructor and explicitly create InstructorEvents. There's also a small typo in your EvalMethodEnum function.

This should work:

this.Events.forEach((element) => {
    element = new InstructorEvent(element.EventId, element.EvaluationMethod);
    console.log(element.EvalMethodEnum);
});

export class InstructorEvent {
    EventId: number;
    EvaluationMethod: number;

    constructor(eventId: number, evaluationMethod: number) {
        this.EventID = eventID;
        this.EvaluationMethod = evaluationMethod;
    }

    get EvalMethodEnum(): EvaluationMethodEnum {
        return EvaluationMethodEnum[this.EvaluationMethod];
    }
}

Or for a simpler approach, you could just eliminate the EvalMethodEnum call and do this instead:

this.Events.forEach((element: InstructorEvent) => {
    console.log(EvaluationMethodEnum[element.EvaluationMethod]);
});