CODEWITHSUNDEEP
typescript
Aidan
Aidan

Reputation: 96

"Cannot read property 'name' of undefined" when it should be defined

interface IField {
  readonly name : string;
  readonly value : string;
  readonly inline ?: boolean;
}

class Field implements IField {
  readonly name : string;
  readonly value : string;
  readonly inline ?: boolean;

  constructor(data : IField) {
    this.name = data.name;
    this.value = data.value;
    this.inline = data.inline;
  }
}

When trying to initialize a new variable from the Field class inside another class like so,

class Embed implements IEmbed {
  ...

  constructor(data : IEmbed) {
    ...

    this.fields = data.fields.map((field) => new Field(field));

    ...
  }
}

My program crashes with the error,

        this.name = data.name;
                         ^

TypeError: Cannot read property 'name' of undefined

If I log the value of data inside the constructor(...) method for Field, it prints out the object without any issue (changed values for privacy),

{
  value: '...message...',
  name: '...name...',
  inline: false
}

But it still crashes. The value given to the Embed constructor is a parsed JSON object from a websocket, and thus the same is true for the Field constructor.

Upvotes: 0

Views: 345

Answers (1)

Aidan
Aidan

Reputation: 96

Ended up using the solution from this question.

class Field implements IField {
  readonly name : string;
  readonly value : string;
  readonly inline ?: boolean;

  constructor(data : Partial<Field> = {}) {
    Object.assign(this, data);
  }
}

I replaced the data : any portion with data : Partial<Field> = {}, providing a default for the field. Thanks to Wiktor for steering me in the right direction.

Upvotes: 1

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