Getting One Property Value From Dictionary Based Upon Another Property Value

Question

I have this expression rule and I need to get the value of one of the keys based upon whether another key property is true or false, I have this but doesn't work: 
 a!localVariables(
 local!myDictionary: {
 {
 item: 1,
 active: true,
 description: "Widget",
 color: "Green"}
 ,{
 item: 2,
 active:false,
 description: "another",
 color: "red"}
 },
 if(
 fn!index(local!myDictionary,"active","") == true,
 fn!index(local!myDictionary,"color",null), "")
) 
 To explain further: I would want to return the value "Green" from the key property color due to active property being true and not the value "red" because active property is false.

Stewart Burchell · Accepted Answer

Hi 
 Here's the code: 
 
 a!localVariables(
 local!myDictionary: {
 {
 item: 1,
 active: true,
 description: "Widget",
 color: "Green"
 },
 {
 item: 2,
 active: false,
 description: "another",
 color: "red"
 }
 },
 local!myDictionary.color[fn!wherecontains(true,fn!toboolean(local!myDictionary.active))]
) 
 Here's the result: 
 
 ...and here's an explanation: 
 
 you can address elements in an array using the square brackets 
 ...so we're looking to extract all of the color attribute values - addressed using local!myDictionary.color - where the corresponding 'active' attribute is true... 
 ...so we use the function 'wherecontains()' which returns the indices in an array that contain the the provided value. So, in our case, fn!wherecontains(true,<the array of local!myDictionary.active>) 
 the expression inside the square brackets returns the indices and is then used to return the values for the array that the square brackets are attached to 
 
 Hope this helps

Josh · Answer

Close. There are a couple of notes. You should use a!map() instead of dictionaries to help resolve typing mismatch errors. With a dictionary you are probably getting a compare error with a list of variant and boolean. so that line should be more like 
 if(toboolean(fn!index(local!myDictionary,"active","")), 
 Note: "if(predicate = true," and "if(predicate," are logically the same 
 Line 15 will give you a boolean array of the indices where "active" is true, but wherever you return false, you will get "" returned, so your snippet would return {"Green", ""}. You could store this result and filter out the nulls using filter() or a!forEach(), but I would write this like: 
 a!localVariables(
 local!myDictionary: {
 a!map(
 item: 1,
 active: true,
 description: "Widget",
 color: "Green"
 ),
 a!Map(
 item: 2,
 active:false,
 description: "another",
 color: "red"
 )
 },
 index(local!myDictionary.color, where(local!myDictionary.active), {})
)

Getting One Property Value From Dictionary Based Upon Another Property Value

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