How to filter some data in memory (without DB queries)

Question

Hi, 
 I'm coding a simple CRUD sub-interface that is integrated inside a parent interface : A grid displays the lines of the table, and each line contains buttons to edit or remove lines. There is another button to allow to add lines in the Grid. 
 All theses actions are made in memory through a Rule Input to store data. At the end, and only at the end, the process store the data in the DB. 
 Now I would need to filter the lines in the grid (ex : display Docs only, or Photos only) but I need to still do it in memory. 
 Example: 
 # Mark Model Doc 1 Wolwagen Golf document 2 Wolwagen Polo photo 3 Nissan Titan photo 4 Nissan Armada document 
 
 To simulate filters, is there any way to do it with Rule Inputs function or mecanism? (I can't use DB query filters). Is there any way do it without storing the data in 2 differents RI (RI_Docs and RI_Photos) ? 
 I would need for example a "Show line when" grid attribute, or a way to memory filter the RI... 
 If you have any idea? 
 Regards

Mike Schmitt · Accepted Answer

You should be able to accomplish this fairly easily via local variables and your basic Appian array functions . 
 Edit: attaching one-form example using all local variables. local!cars can simply be swapped out with a rule input of your needed CDT type, then adjust the property names as needed. a!localVariables(
 local!cars: {
 a!map(id: 1, brand: "vw", model: "golf", doc: "document"),
 a!map(id: 2, brand: "vw", model: "polo", doc: "photo"),
 a!map(id: 3, brand: "nissan", model: "titan", doc: "photo"),
 a!map(id: 4, brand: "nissan", model: "armada", doc: "document")
 },
 
 local!filterChoices: {"document", "photo"},
 local!filterValue: null(),
 
 local!filteredSelection: if(
 isnull(local!filterValue),
 local!cars,
 index(
 local!cars,
 wherecontains(
 local!filterValue,
 local!cars.doc
 ),
 local!cars
 )
 ),
 
 
 a!formLayout(
 label: "Cars Grid",
 
 contents: {
 a!dropdownField(
 choiceLabels: local!filterChoices,
 choiceValues: local!filterChoices,
 placeholder: "-- filter by attachment type --",
 value: local!filterValue,
 saveInto: local!filterValue
 ),
 
 a!gridField(
 data: local!filteredSelection,
 columns: {
 a!gridColumn(
 label: "Brand",
 value: fv!row.brand
 ),
 a!gridColumn(
 label: "Model",
 value: fv!row.model
 ),
 a!gridColumn(
 width: "NARROW",
 helpTooltip: "Attachment Type",
 value: fv!row.doc
 )
 }
 )
 }
 )
)