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

HiHere'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 toHope this helps

joshl · 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), {})
)

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