Multiple Mixins for custom blocks

[shane-lab]

At the moment you can not assign multiple mixins to a custom block.

In my solution I have a particular behaviour that I want some blocks to have. Mixins are a great way to add those behaviours to these blocks, however there are some cases where I would like other blocks to have additional behaviours too.

It would be great if the extensions property could accept multiple Mixins.

spoiler

Blockly.Extensions.registerMixin('a', mixinA);
Blockly.Extensions.registerMixin('b', mixinB);

Blockly.Blocks["blockA"] = {
  init: function () {
    this.jsonInit({
      extensions: ['a'],
    });
  }
};

Blockly.Blocks["blockB"] = {
  init: function () {
    this.jsonInit({
      extensions: ['a', 'b'],
    });
  }
};

Then it would be great if it is possible to run the events of the mixin in serial. Right now I have to create said mixin combinations manually e.g.:

const combineMixins = mixins => {
  const suppressPrefixSuffix = mixins.reduce((acc, mixin) => acc || mixin.suppressPrefixSuffix, false);
  const changeHandlers = mixins.reduce((acc, mixin) => {
    if (typeof mixin.onchange === 'function') {
      acc.push(mixin.onchange);
    }
    return acc;
  }, []);
  const onchange = function(...args) {
    changeHandlers.forEach(handler => handler.bind(this)(...args));
  };
  
  return { suppressPrefixSuffix, onchange };
};

Blockly.Extensions.registerMixin('a', mixinA);
Blockly.Extensions.registerMixin('b', mixinB);
Blockly.Extensions.registerMixin('c', mixinC);
Blockly.Extensions.registerMixin('a+b', combineMixins(mixinA, mixinB));
Blockly.Extensions.registerMixin('a+c', combineMixins(mixinA, mixinC));
Blockly.Extensions.registerMixin('a+b+c', combineMixins(mixinA, mixinB, mixinC));
Blockly.Extensions.registerMixin('b+c', combineMixin(mixinB, mixinC));
...etc

I think a Block will benefit of the possibility of having multiple mixins, e.g. support multiple "inheritance". What are your opinions on this proposal? Or is there an existing solution to the above that I have not discovered yet?

Thanks for reading!

[maribethb]

Hello,

We already do support multiple mixins in the same block. As far as I know the code in your spoiler tag in the original post should work. Here's an example of using multiple mixins.

So I'm going to close this but if you find that the code isn't working please reopen or post on our developer forum for help. Thanks!