2.2 KiB
Custom object types
Touch Develop docs for the @boardname@.
What is an object?
An object allows you to bundle several related pieces of data. For instance, if you have a player on the screen, there are two pieces of data that make up the object: its x position, and its y position. Therefore, we will define a player to be an object with two fields: the x field and the y field. By grouping related variables together in a single object, you reduce confusion in your script and eliminate some errors.
What is an object type?
In order to use objects, we must first define an object type. More concretely, in order to create a new player, we must define what a player is. In our case, the type of players is the type of objects with two fields x and y of type Number.
Creating an object type is done in the following manner. Hit "add new", then hit "object type".
(picture foobar2)
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You can change the name of the type by clicking on it (i.e. replace Thing with Player). You can also add two fields of type number. Once this is done, here's what you should see.
We have now defined what a player is (it has an x field and a y field). Player is a type, just like Number and String. However, we have not created any player yet.
Creating objects and using them
To create a new variable of a given type, you can call the create operation on Player.
let p = new Player()
Just like var x := 3 creates a new variable (x) of type Number, the line above creates a new variable (p) of type Player. We say that p is an instance of Player.
If you want to modify (mutate) p, here's how you do it.
p.x = 5
You can read the fields of p as follows.
basic.showString("My player is at x = ", 150)
basic.showNumber(p.x, 150)
That is, the generic syntax for accessing a field x of an object p is p → x.
If there are multiple players in your game, you may want to create a collection of them.
let c = (<Player[]>[])
c.push(new Player())
A good example of using objects is in the game pac-man runaway. Search for it, read it and clone it!