7. Link integrity for blocks

Using the latest plone.restapi, Volto blocks also provide Link Integrity protection (if you have references to other internal content, removing the destination object triggers a validation rule).

By default the href and url fields of any block data is used to establish the link integraty protection. You can define additional fields, or other extraction methods, by writing a subscriber for plone.restapi.interfaces.IBlockFieldLinkIntegrityRetriever.

For example:

@adapter(IBlocks, IBrowserRequest)
@implementer(IBlockFieldLinkIntegrityRetriever)
class GenericBlockLinksRetriever(object):
    order = 1
    block_type = None

    def __init__(self, context, request):
        self.context = context
        self.request = request

    def __call__(self, block):
        """
        Returns a list of internal links
        """
        links = []
        for field in ["url", "href"]:
            value = block.get(field, "")
            if value and "resolveuid" in value:
                links.append(value)
        return links

  <subscriber
      factory=".blocks_linkintegrity.GenericBlockLinksRetriever"
      provides="plone.restapi.interfaces.IBlockFieldLinkIntegrityRetriever"
      />