Tips for assigning values to a nested array in Angular object creation

Question

Tips for assigning values to a nested array in Angular object creation

Here are the definitions for the Conversation and Message models I am implementing in my Ionic 5 / Angular application:

export class Conversation {
    constructor(
        public id: string,
        public userId: string,
        public mechanicId: string,
        public messages: Message[]
    ) { }
}

Below is the structure of the Message model:

export class Message {
    constructor(
        public id: string,
        public text: string,
        public userId: string,
        public timestamp: string
    ) { }
}

When a user creates a new Conversation instance, they should include one Message object within the Conversation.

Subsequently, if other users are updating the Conversation (e.g. sending more messages), they will simply add another Message to the existing Conversation.

This is how I currently handle the creation of a Conversation:

onSendMessage() {
    this.conversationService.addConversation(
        this.mechanicToContact.id,
        this.form.value.message
    );
}

I've attempted the following approach within my ConversationService:

addConversation(mechanicId: string, message: string) {
    const newConversation = new Conversation(
      Math.random().toString(),
      this.authService.userId,
      mechanicId,
      [new Message(Math.random().toString(), message, this.authService.userId, mechanicId)]
      );
  }

However, I encounter an error when trying to create a new Message:

An argument of type 'Message' cannot be assigned to a type parameter of 'Message[]'

I am uncertain about how to pass the remaining attributes of the Message correctly. Can someone guide me through this process?

angular typescript

Answer 1

Answer №1

The Conversation class is looking for an array of messages, but you are providing a single message. One way to address this issue is by wrapping the message in an array like so:

const newConversation = new Conversation(conversationId, userId, mechanicId, [ message ]);

This solution encapsulates the message within an array.

Alternatively, you can modify the Conversation class as shown below to handle both single and multiple messages correctly:

export class Conversation {
    public messages: Message[];

    constructor(
        public id: string,
        public userId: string,
        public mechanicId: string,
        messages: Message | Message[]
    ) { 
      this.messages = Array.isArray(messages) ? messages : [ messages ];
    }

    addMessages(messages: Message | Message[]): void {
       this.messages.push(
          ...(Array.isArray(messages) ? messages : [ messages ])
       );
    }
}

This updated class can accommodate both singular and multi-message inputs.

In practice, it's often best to delegate this functionality to a service. Here's an example of how you could implement a ConversationService:

export interface Conversation {
  id: string;
  userId: string;
  mechanicId: string;
  messages: Message[];
}

@Injectable({
  providedIn: 'root'
})
export class ConversationService {
  private conversations: Conversation[];

  addConversation(mechanicId: string, message: string): Conversation {
    const conversation: Conversation = {
      id: getUniqueUid(), // unique identifier generation
      userId: this.userService.getUserId(), // retrieve user ID method
      mechanicId,
      messages: [ this.createMessage(message) ] 
    };

    this.conversations.push(conversation);

    return conversation;
  }

  addToConversation(id: string, mechanicId: string, message: string): Conversation {
    const conversation = this.getConversation(id);

    if (conversation) {
      conversation.messages.push(
        this.createMessage(message)
      );
    }

    return conversation;
  }

  private createMessage(message: string): Message {
    return {
      id: getUniqueMid(), // unique message ID generation
      text: message,
      userId: this.userService.getUserId(),
      timestamp: Date.now()
    };
  }

  private getConversation(id: string): Conversation | undefined {
    return this.conversations.find((conversation) => conversation.id === id); 
  }
}

Answer 2

The Conversation class is looking for an array of messages, but you are providing a single message. One way to address this issue is by wrapping the message in an array like so:

const newConversation = new Conversation(conversationId, userId, mechanicId, [ message ]);

This solution encapsulates the message within an array.

Alternatively, you can modify the Conversation class as shown below to handle both single and multiple messages correctly:

export class Conversation {
    public messages: Message[];

    constructor(
        public id: string,
        public userId: string,
        public mechanicId: string,
        messages: Message | Message[]
    ) { 
      this.messages = Array.isArray(messages) ? messages : [ messages ];
    }

    addMessages(messages: Message | Message[]): void {
       this.messages.push(
          ...(Array.isArray(messages) ? messages : [ messages ])
       );
    }
}

This updated class can accommodate both singular and multi-message inputs.

In practice, it's often best to delegate this functionality to a service. Here's an example of how you could implement a ConversationService:

export interface Conversation {
  id: string;
  userId: string;
  mechanicId: string;
  messages: Message[];
}

@Injectable({
  providedIn: 'root'
})
export class ConversationService {
  private conversations: Conversation[];

  addConversation(mechanicId: string, message: string): Conversation {
    const conversation: Conversation = {
      id: getUniqueUid(), // unique identifier generation
      userId: this.userService.getUserId(), // retrieve user ID method
      mechanicId,
      messages: [ this.createMessage(message) ] 
    };

    this.conversations.push(conversation);

    return conversation;
  }

  addToConversation(id: string, mechanicId: string, message: string): Conversation {
    const conversation = this.getConversation(id);

    if (conversation) {
      conversation.messages.push(
        this.createMessage(message)
      );
    }

    return conversation;
  }

  private createMessage(message: string): Message {
    return {
      id: getUniqueMid(), // unique message ID generation
      text: message,
      userId: this.userService.getUserId(),
      timestamp: Date.now()
    };
  }

  private getConversation(id: string): Conversation | undefined {
    return this.conversations.find((conversation) => conversation.id === id); 
  }
}

Answer 3

Answer №2

Make sure to update your addConversation function with the following code snippet:

addConversation(userId: string, mechanicId: string, messages: Message[]) {
    const newConversation = new Conversation(conversationId, userId, mechanicId, messages);
  }

Ensure that you are passing an array of messages as a parameter in the conversation class constructor.

Answer 4

Make sure to update your addConversation function with the following code snippet:

addConversation(userId: string, mechanicId: string, messages: Message[]) {
    const newConversation = new Conversation(conversationId, userId, mechanicId, messages);
  }

Ensure that you are passing an array of messages as a parameter in the conversation class constructor.

Tips for assigning values to a nested array in Angular object creation

Answer №1

Answer №2

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