CODEWITHSUNDEEP
javascripttypescript
Rolando
Rolando

Reputation: 762

Use of "this" in typescript class

I am working with some refactoring of typescripts clases related with dataContext. The thing is yesterday i spent a lot of time trying figure out why i was not getting a breeze.promise from my new datacontext. finally i got the solution and it was related with the scope of "this". Example of bad use of "this":

public getSomething(){
  return this.manager.executeQuery(query)
        .then(function (data) {               
          //THIS IS NOT WORKING" INSIDE OF THE FUNCTION
            this.log('this log will never be loged :(');
        }
}

Now the same code working fine, but using a "that" as temp variable:

public getSomething(){
  var that=this;
  return this.manager.executeQuery(query)
        .then(function (data) {               
            that.log('get something is complete');
        }
}

if you see in abore the second piece of code is working fine, but i have to repeat the process for every method in my class. Now my question is: How can i create a "that" variable at class level? is that possible?

I tried with the code bellow but i am getting a compilation error:"Could not find symbol 'that'."

 export class eventDataContext extends dataContextBase.dataContextBase {
    public that;

    constructor() {        
      super();
      that = this;
    ...
    }
 }

any idea how to put this new variable "that" at class level? thank you!

Upvotes: 1

Views: 186

Answers (1)

Fenton
Fenton

Reputation: 250812

TypeScript has a handy shortcut to solve this problem, called "fat arrow syntax" =>

If you use the following, it should work for you:

getSomething(){
  return this.manager.executeQuery(query)
        .then((data) => {               
            this.log('This *will* now be logged :)');
        });
}

Quick disclaimer - I'm not sure where your query is coming from - it isn't passed into the getSomething method. If it is a class property, use this.query.

Upvotes: 3

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