_checkList

Display a checklist of items to add or remove from a Set. -- Function

Thing Type -> Thing Type._checkList (on, selectedOnly, display, filterField, addModel) -> The same Type

Receives -- Thing Type: The items to choose from. : Defining Context : The Property that actually contains the checklist, which should be a Set of Things
on: The Thing that contains the Set.
selectedOnly (optional): If True, only items currently in the Set will be displayed.
display (optional): How to display each item.
filterField (optional): If specified, the ID of a text field to filter on
addModel (optional): If specified, you can type names in the filterField, and new Instances of this Model will be created
Produces: The Check List, ready to display.

Sometimes, you want to be able to take a Set, and use it as a checklist. The _checkList function is designed for that.

For example, say that you have a Shopping List Space. There is a Shopping Item Model, with an Instance for each item that you sometimes shop for, and a Shops Tag Set saying where it can be found. You have a Thing named "Shopping List", with a Property "Contents", which is a Set of Things. You would display the whole shopping list, as a checklist, like this:

[[Shopping Item._instances -> Contents.checkList(on = Shopping List)]]

That is, the actual list is found in Shopping List.Contents, and you are choosing from all Instances of Shopping Item. This lets you easily add Items to the list.

Sometimes, you only want to list the items that are actually checked-off. For example, when you go shopping, you just want to be checking things off the list. So you would say:

[[Shopping Item._instances -> Contents._checkList(on = Shopping List, selectedOnly = true)]]

By using selectedOnly like this, it will only display the currently-selected Items, so you can check them off.

You can filter which items show on the list. For instance, you could show a list of just the Items to look for at Acme like this:

[[Shopping Item._instances
  -> _filter(Shops -> _contains(Acme))
  -> Contents._checkList(on = Shopping List, selectedOnly = true)]]

This way, you can easily display customized checklists for particular situations.

You can also create a live filter-by-name. If you specify the filterField parameter, that should point to a _textInput that you can type into, to filter down the items being currently shown in the checklist.

You can also use the filterField to add new items. If you add the addModel parameter, that specifies the model for the items in this list; if you type in a new name in the filterField and press Enter, a new instance of that model will be created, with the given name, and added to the checklist.

So putting those together, you can specify a full shopping list, that lets you filter the items being shown and add new one on the fly, like this:

[[_textInput(id = ""itemfilter"", placeholder = ""Filter or add items"")]]

[[Shopping Item._instances ->
  Shopping Items._checkList(on = Shopping List, filterField = ""itemfilter"", addModel = Shopping Item)]]

By default, _checkList will display show each item's Name. But you can customize this using the display parameter. If provided, this will be applied to every item, and the result is what will be shown.