title: Ant Design Dynamic field validation
body: <p>Im trying to create dynamic field validator - when "isDisable" is true then it is not required + no need to check number type.</p>
  
  <pre><code>{getFieldDecorator('number', {
    validateFirst: true,
    rules: [{
      required: !isDisable,
      message: 'Must enter data'
    }, {
      type: 'number',
      message: 'Need to enter number'
    }]
  })(
    &lt;InputNumber min={0} step={1} disabled={isDisable} /&gt;
  )}
  </code></pre>
  
  <p>But this code still checks number type.</p>
  
  <p>I also tried this in render function:</p>
  
  <pre><code>const rules = isDisable ? { } : {
    validateFirst: true,
    rules: [{
      required: true,
      message: 'Must enter data'
    }, {
      type: 'number',
      message: 'Need to enter number'
    }]
  };
  
  {getFieldDecorator('number', rules)(
    &lt;InputNumber min={0} step={1} disabled={isDisable} /&gt;
  )}
  </code></pre>
  
  <p>But when entering data the validator only occurs when "validateFieldsAndScroll" function called, and I want it to validate onChange event</p>
  
  <p>So how can I create a rule that doesn't check the type if the field is disabled?</p>
  
  <p>Thank.</p>