num_children interface

This page explains the container class, like the Graphics, Sprite, Stage) num_children property interface.

What interface is this?

The num_children property interface returns the integer (Int) value of the number of children.

Notes

The Sprite instance’s initial children number is 1, not 0 since a sprite instance has a graphics child.

Basic usage

The num_children property returns the number of children (Int value). You can use it for the calculation, for instance, coordinates calculation.

The following example appends a new rectangle when you click the sprite (rectangle) instance. The num_children property determines a new rectangle x-coordinate. When clicking a rectangle, this code also displays the current num_children property value to the browser console (please press the F12 key).

import apysc as ap


def on_sprite_click(e: ap.MouseEvent[ap.Sprite], options: dict) -> None:
    """
    The handler that the sprite calls when clicked.

    Parameters
    ----------
    e : MouseEvent
        Event instance.
    options : dict
        Optional arguments dictionary.
    """
    sprite: ap.Sprite = e.this
    rectangle_x: ap.Int = (sprite.num_children - 1) * 100 + 50
    new_rect: ap.Rectangle = sprite.graphics.draw_rect(
        x=rectangle_x, y=50, width=50, height=50
    )
    sprite.add_child(new_rect)
    ap.trace(
        "Current sprite children number:",
        sprite.num_children,
        "rectangle x:",
        rectangle_x,
    )


ap.Stage(
    background_color=ap.Color("#333"),
    stage_width=450,
    stage_height=150,
    stage_elem_id="stage",
)

sprite: ap.Sprite = ap.Sprite()
sprite.graphics.begin_fill(color=ap.Color("#0af"))
rectangle_1: ap.Rectangle = sprite.graphics.draw_rect(x=50, y=50, width=50, height=50)
sprite.add_child(rectangle_1)
sprite.click(on_sprite_click)

ap.save_overall_html(dest_dir_path="num_children_basic_usage/")

num_children API

Note: the document build script generates and updates this API document section automatically. Maybe this section is duplicated compared with previous sections.

[Interface summary]

Get a current children’s number.

[Returns]

  • num_children: int

    • Current children number.

[Examples]

>>> import apysc as ap
>>> stage: ap.Stage = ap.Stage()
>>> sprite: ap.Sprite = ap.Sprite()
>>> sprite.graphics.begin_fill(color=ap.Color("#0af"), alpha=0.5)
>>> rectangle_1: ap.Rectangle = sprite.graphics.draw_rect(
...     x=50, y=50, width=50, height=50
... )
>>> rectangle_2: ap.Rectangle = sprite.graphics.draw_rect(
...     x=150, y=50, width=50, height=50
... )
>>> sprite.graphics.num_children
Int(2)