Hello Julian,
Sadly the validator doesn't get automatically connected :/ you need to manually connect it using
these documented methods. The reason it doesn't get automatically connected is to allow you to have multiple fields with multiple different validators.
For your situation, since you're using a json definition, you'll probably want to do something like this:
```
Blockly.Blocks['newBlock'] = {
init: function() {
this.jsonInit(myJsonDef);
this.getField('MY_CHECKBOX_FIELD_NAME').setValidator(this.validate_.bind(this));
},
validate_: function() { /* my custom logic */ }
}
```
I hope that helps! If you have any further questions please reply!
--Beka