ocular rewritten

NitroCipher wrote:

Creating extensions for Scratch 3.0

There is now official documentation regarding extensions!, but feel free to use this post to get you started

You'll want to start off by creating your extension's class, and register the extension - In my case, this would be ‘NitroBlock’

class NitroBlock { //In both instances, NitroBlock will be the name in both instances
}
Scratch.extensions.register(new NitroBlock());

Next, we will be constructing block and menu definitions - We will continue to use ‘NitroBlock’ through this tutorial

getInfo() {
    return {
        "id": "NitroBlock",
        "name": "NitroBlock",
        "blocks": [
        ],
        "menus": { //we will get back to this in a later tutorial
        }
    };
}

We are going to take a look at how blocks are constructed

For those of you that are familiar with extensions for Scratch 2.0, we will start off with this: - If not, you can ignore this

['r', 'letters %n through %n of %s', 'substringy', '2', '5', 'hello world']
//breakdown below:
['r' = block type, 'letters %n through %n of %s' = block text, 'substringy' = block ID/opcode]

{
    "opcode": "substringy", //This will be the ID code for the block
    "blockType": "reporter", //This can either be Boolean, reporter, command, or hat
    "text": "letters [num1] through [num2] of [string]", //This is the block text, and how it will display in the Scratch interface
    "arguments": { //Arguments are the input fields in the block. In the block text, place arguments in square brackets with the corresponding ID 
        "num1": { //This is the ID for your argument
            "type": "number", //This can be either Boolean, number, or string
            "defaultValue": "2" //This is the default text that will appear in the input field, you can leave this blank if you wish
        },
        "num2": {
            "type": "number",
            "defaultValue": "5"
        },
        "string": {
            "type": "string",
            "defaultValue": "hello world"
        }
    }
},

We will put this newly constructed code into the blocks object above - My code will now look like this

class NitroBlock {
    getInfo() {
        return {
            "id": "NitroBlock",
            "name": "NitroBlock",
            "blocks": [{
                    "opcode": "substringy",
                    "blockType": "reporter",
                    "text": "letters [num1] through [num2] of [string]",
                    "arguments": {
                        "num1": {
                            "type": "number",
                            "defaultValue": "2"
                        },
                        "num2": {
                            "type": "number",
                            "defaultValue": "5"
                        },
                        "string": {
                            "type": "string",
                            "defaultValue": "hello world"
                        }
                    }
                },
            }],
        "menus": { //we will get back to this in a later tutorial
        }
    };
}
Scratch.extensions.register(new NitroBlock());

Next we come to the most important part, the code that actually runs the blocks! - I am keeping this short and simple for tutorial's sake.

//Make sure you name this function with with the proper ID for the block you defined above
substringy({num1, num2, string}) { //these names will match the argument names you used earlier, and will be used as the variables in your code
    //this code can be anything you want
    return string.substring(num1 - 1, num2);  //for reporters and Boolean blocks the important thing is to use 'return' to get the value back into Scratch.
}

Place this new code below your getInfo() function

class NitroBlock {
    getInfo() {
        return {
            "id": "NitroBlock",
            "name": "NitroBlock",
            "blocks": [{
                    "opcode": "substringy",
                    "blockType": "reporter",
                    "text": "letters [num1] through [num2] of [string]",
                    "arguments": {
                        "num1": {
                            "type": "number",
                            "defaultValue": "2"
                        },
                        "num2": {
                            "type": "number",
                            "defaultValue": "5"
                        },
                        "string": {
                            "type": "string",
                            "defaultValue": "hello world"
                        }
                    }
                },
            }],
        "menus": { //we will get back to this in a later tutorial
        }
    };
    substringy({num1, num2, string}) {
        return string.substring(num1 - 1, num2);
    };
}

Save this code to your computer as a js file, in my case it is NitroBlock_3.js

Congratz, you now have your extension code created!!
You can use this tutorial to add it your own personal copy of scratch
Or, you can host the extension with gh-pages, and go here to test it (provide your own url, don't use mine)

Here is the archived copy of my original post