How to update the menu of a dropdown Field

[Jakob Krause]

Hello there,

I am currently working on a project where the menu of a dropdown field is an array which may be modified. Now if I rename one element I need to select the renamed option on all blocks.

My goal is that the menu gets updated in the same instance I update my array plus the dropdown field should select the option with the same index as before. Do you know how I can code this?

Many thanks in advance

Jakob Krause 

[Jason Schanker]

Hi Jakob,

Do all the dropdowns share the same Array of options?  If so, the easiest way is to initialize a variable to your options Array and reference that Array in your block definition:

const workspace = Blockly.getMainWorkspace();

const optionsArr = [['Default option', 'DEFAULT'], ['Option B', 'OPTIONB'], ['Option C', 'OPTIONC']];

let currentOptionsArr = optionsArr.slice(); // used for comparison

Blockly.Blocks['sharedOptionsBlock'] = {

  init: function() {

    this.appendDummyInput().appendField(new Blockly.FieldDropdown(optionsArr), 'OPTS');

  }

};

If the renaming of an option only occurs on a workspace event, you could add a listener to the workspace to do a comparison of currentOptionsArr to optionsArr.  If there was a change, you can iterate over all the blocks of the specified type, selecting the appropriate new field value based on the differing index and then update the currentOptionsArr to be a (shallow) copy of optionsArr.

workspace.addChangeListener((e) => {

  const changedIndex = optionsArr.findIndex((option, index) => option[0] !== currentOptionsArr[index][0] || option[1] !== currentOptionsArr[index][1]);

  if (changedIndex !== -1) {

    Blockly.getMainWorkspace().getBlocksByType('sharedOptionsBlock').forEach(b => {
      b.setFieldValue(optionsArr[changedIndex][1], 'OPTS')
    });

    currentOptionsArr = optionsArr.slice();

  }

});

Best,

Jason

[Beka Westberg]

Hello Jakob,

You might also be able to use a variable field for this. They're called variable fields, but really they're just identifier fields. They automatically handle renamings and updating other relevant dropdowns. And if you're using variable fields elsewhere, you can always add a type filter, so that only the specific ones you want to show show up.

But if you don't want the names to be editable by users, then it probably won't work for your case.

Best of luck on your project!
--Beka

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