Referencing List items

How To
1

Referencing List items

When working with a ListTYP , you are able to reference specific items in lists by using the below expression:

= mylist[#index#].item_property

This #index# refers the position of the item in the list and must be a IntegerTYP .

Note: All list iterations start from [0] that is to say the 1st item in a list would be referenced with mylist[0] and the 2nd item with mylist[1] etc.

However, you are only able to use the above expression when extracting certain values from a list, lets say, retrieving the first or last item in a list.

:floppy_disk: Sample Solutions
Unique values are counted and updated in a list in the solutions.
Linx 5.22.0 Solution.lsoz (5.5 KB)
Linx 6.0.5 Linx6.zip (6.2 KB)

Update specific list items

In order to set or update values of a list, you must use a ForEachFNC like below:

Let’s say you have a list like below:

[
   {
      "Name":"a",
      "Quantity":3
   },
   {
      "Name":"b",
      "Quantity":2
   },
   {
      "Name":"c",
      "Quantity":1
   },
   {
      "Name":"d",
      "Quantity":2
   }
]

And now you want to update the Quantity value of the item with the Name of “c”.

This would be done by looping through the list using a ForEachFNC . On each iteration, a condition would then be evaluated (using an IfElseFNC ) that checks if the current loop item is equal to a value such as “c” , like the below:

= ForEach.Loop.Name== "c"

If the condition is met, a SetValueFNC is used to set the current ForEach.Loop.Quantity value like below:

Target : = ForEach.Loop.Quantity

Source : = ForEach.Loop.Quantity+1

In this case, a Quantity field of a list item is increased.

This will mean that the item in the list of the current iteration will be updated with a new value.

image

A list (ListA) contains multiple non-distinct characters like the below:

["a","b","a","a","b","c","d","d"]

A list (ListB) contains the structure like below:

[ {"Name": "x" , "Quantity" : 0  } ]

The ListA is looped through (ForEach_ListA).

For each item in ListA, a BooleanTYP (CheckIfFound) is reset to False, this will contain the result of whether or not then item already exists in ListB.

For each item in ListA, a loop is then performed on ListB (ForEach_ListB) which filters for an item with the Name matching the current item of ListA i.e. “a”, “c” ,“d” etc ,with the below expression:

= ForEach_ListA.Loop == ForEach_ListB.Loop.Name

If the condition is met, the Quantity value of the current ListB item is then increased with a SetValueFNC .

Target : = ForEach_ListB.Loop.Quantity
Source : = ForEach_ListB.Loop.Quantity + 1

The value of CheckIfFound is then set to True.

If the value of CheckIfFound is equal to False, then a new list item is added to ListB.

The result will be ListB will be the below:

[
   {
      "Name":"a",
      "Quantity":3
   },
   {
      "Name":"b",
      "Quantity":2
   },
   {
      "Name":"c",
      "Quantity":1
   },
   {
      "Name":"d",
      "Quantity":2
   }
]