Arguments and their Types

note

Anything that only works unsandboxed will be noted, but regardless, we will assume you are creating an unsandboxed extension during this tutorial.

So far we have created a regular command block, reporter block, and a boolean block.
But none of these blocks actually allow us to put other blocks inside, or even really do anything useful.

Why don't we take a look at handling block arguments?

How do we add an input to a block?

First we need to start by adding an arguments object to a block.
Let's use our console logging block for this.

[
  {
    opcode: 'logToConsole',
    text: 'log to console',
    blockType: Scratch.BlockType.COMMAND,
    arguments: {}
  }
]

Next we need to add a property to this object. The value will be another object.
It's recommended to use an all-capitals name, like so:

[
  {
    opcode: 'logToConsole',
    text: 'log to console',
    blockType: Scratch.BlockType.COMMAND,
    arguments: {
        TEXT: {}
    }
  }
]

Now we need to decide where the block should show this input.
If we want the argument to appear after the word "log" like so,

then we'll need to surround the argument key in square brackets ([TEXT]) and place it after the word "log" in the text property:

[
  {
    opcode: 'logToConsole',
    text: 'log [TEXT] to console',
    blockType: Scratch.BlockType.COMMAND,
    arguments: {
        TEXT: {}
    }
  }
]

We are nearly there, we just need to define the type of the argument.
This determines whether we can accept letters, only numbers, colors, and for that we need to go into:

Argument Types

Argument types define what our argument can take as an input. See Here for all keys an argument can take. You can set an argument's type by setting the type property in the argument to a Scratch.ArgumentType.
Here is a list of all the available argument types:

	Value	Explanation
Scratch.ArgumentType.ANGLE	'angle'	Numeric value with angle picker
Scratch.ArgumentType.BOOLEAN	'Boolean'	Boolean value with hexagonal placeholder
Scratch.ArgumentType.COLOR	'color'	Numeric value with color picker
Scratch.ArgumentType.NUMBER	'number'	Numeric value with text field
Scratch.ArgumentType.STRING	'string'	String value with text field
Scratch.ArgumentType.MATRIX	'matrix'	String value with matrix field
Scratch.ArgumentType.NOTE	'note'	MIDI note number with note picker (piano) field
Scratch.ArgumentType.IMAGE	'image'	Inline image on block (as part of the label)
Scratch.ArgumentType.POLYGON	polygon	pm: creates an input with an indefinite number of x,y inputs
Scratch.ArgumentType.COSTUME	'costume'	Costume menu (taken from tw)
Scratch.ArgumentType.SOUND	'sound'	Sound menu (taken from tw)