Typescript interface type mapping to an object that consists of an original object and a new object built from original object's fields

Question

I would like to map a type X to another type Y that consists of X and Z, where Z contains two values of X. Sounds convoluted, so you'll find the code below.

I have a following model for a data object from a database:

export interface Task {
 description: string;
 name: string;
 beginDate: string;
 endDate: string;
}

Having made a call to the DB, I would like to map these objects to the following type:

export interface TaskWithDate {
 task: Task;
 fullDate: FullDate;
}

where FullDate is an interface with the following definition:

export Interface FullDate {
 beginDate: string;
 endDate: string;
}

...and it should be filled with beginDate and endDate from a Task .

So, I make a call to the DB and want to do the mapping:

tasks: Task[];
this.tasks = this.getAllTasks(); // db call
this.ticketsWithDate = this.tasks.map(
      t => { return <TasktWithDate>{ task: t, fullDate: null }}
    );

Question: How can I grab the startDate and endDate of Task ( t ) to create a FullDate object within the map function?

Answer 1

Iterate over the task array as you have done and then map the corresponding fields you need from it to form the TaskWithDate array as illustrated below:

ticketsWithDate: TaskWithDate[];

this.ticketsWithDate = this.tasks.map(
  tsk => {
    return {
      task: tsk,                       // map entire task object
      fullDate: {                      // fetch begin and end dates from task to 
        beginDate: tsk.beginDate,      // form a new key i.e fullDate
        endDate: tsk.endDate
      }
    };
  }
);

Answer 2

It's simple , why don't you try just this,

this.ticketsWithDate = this.tasks.map(
    t => { 
        let fullDate: FullDate = {
            beginDate = t.beginDate,
            endDate = t.endDate
        }

        return <TasktWithDate>{ task: t, fullDate: fullDate }
    }
);

Or this,

this.ticketsWithDate = this.tasks.map(
t => { 
    return <TasktWithDate>{ task: t, fullDate: {
        beginDate = t.beginDate,
        endDate = t.endDate
    }
    }
}

);