Creating an expression rule equivalent to a!queryEntity() but for a list of a!map()

Question

Hi all, 
 The title basically describes it. I'd like to be able to apply filters on a list of maps on their key values. 
 For example in the code snippet below, to be able to set filter("name","=",bill) or filter("name", "not null"). 
 Similar to a!queryEntity but for a collection of map instead of a Entity 
 a!localVariables(
 local!mapCollection: {
 a!map(name: "bill"),
 a!map(name: "bob"),
 a!map(name: "Jim"),
 a!map(name: null)
 }

) 
 
 Also be able to apply operands like and and or if there are multiple key values in the map collection

aditya007 · Accepted Answer

Hope this will resolve the above problem 
 . a!localVariables(
 local!mapCollection: {
 a!map(name: "bill"),
 a!map(name: "bob"),
 a!map(name: "Jim"),
 a!map(name: null)
 },
 local!option1: index(
 local!mapCollection,
 wherecontains({ null, "bill" }, local!mapCollection.name),
 {}
 ),
 local!option2: index(
 local!mapCollection,
 where(
 a!forEach(
 items: local!mapCollection.name,
 expression: a!localVariables(
 local!x: like(fv!item, "*bill*"),
 local!y: like(fv!item, "*ll*"),
 local!z: like(fv!item, "*ill*"),
 and(local!x, local!y, local!z)
 )
 )
 ),
 {}
 ),
 local!option2
)

mikels7956 · Answer

I think you misunderstand my requirement but you helped me find the answer nonetheless. Basing myself on your solution 
 a!localVariables(
 local!mapCollection: {
 a!map(name: "bill", phone: "211"),
 a!map(name: "bob", phone: "311"),
 a!map(name: "Jim", phone: "411"),
 a!map(name: null, phone: "511")
 },
 local!filterName: wherecontains({ null, "bill" }, local!mapCollection.name),
 local!filterPhone: wherecontains({ "911" }, local!mapCollection.phone),
 local!filterIndexes: and(local!filterName,local!filterPhone),
 local!solution: index(
 local!mapCollection,
 local!filterIndexes,
 {}
 ),
 local!solution
)

Peter Lewis · Answer

This is definitely a valid way to do it, but the other approach I often use is to just use a!forEach() and some kind of text function to check to see if it matches or not. For example, you can use the find() function to check if a text string exists in the list. If it doesn't, return an empty list (which then is removed when the list is flattened). a!localVariables(
 local!mapCollection: {
 a!map(name: "bill", phone: "211"),
 a!map(name: "bob", phone: "311"),
 a!map(name: "Jim", phone: "411"),
 a!map(name: null, phone: "511")
 },
 a!flatten(
 a!forEach(
 items: local!mapCollection,
 expression: if(
 find("b", fv!item)>0,
 fv!item,
 {}
 )
 )
 )
)

Creating an expression rule equivalent to a!queryEntity() but for a list of a!map()

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