{"id":1736,"date":"2014-03-22T19:02:52","date_gmt":"2014-03-22T18:02:52","guid":{"rendered":"http:\/\/blog.modelical.com\/?p=496"},"modified":"2024-10-18T08:54:06","modified_gmt":"2024-10-18T06:54:06","slug":"grasshopper-scripting-104","status":"publish","type":"post","link":"https:\/\/www.modelical.com\/en\/grasshopper-scripting-104\/","title":{"rendered":"Grasshopper Scripting 104"},"content":{"rendered":"

Lists<\/h2>\n

In the last post we discussed applying conditional operations<\/a> to single values. But that is way too simple. We expect to process many different values when working with Grasshopper and the power of scripting increases when we deal with collections of data. The main collection type you should care about is The List.<\/p>\n

Download here the GH file (0.9.014) containing the examples.<\/a><\/p>\n

Working With Lists<\/h3>\n

Lists can be created or processed within the scope of a Grasshopper C# scripting component. To access an input parameter as a list we must specify so in the context menu. This will allow us to iterate through all the elements of the list instead of performing the defined operations for each input by default, as happened in the examples in 103.<\/p>\n

\"\"<\/p>\n

Now we can access the list as a whole to, for instance, measure how many elements are there in the list with the Count property.<\/p>\n

 private void RunScript(List<double> x, ref object A)\r\n  {\r\n     A = String.Format(\"There are {0} elements in the list\", x.Count);\r\n  }<\/pre>\n
\"\"<\/p>\n
Declaring Lists<\/strong><\/h3>\n
In order to process a list we are going to need a bit more of flow control than just conditionals<\/a>\u00a0but before diving into loops let’s see how to declare and populate a list inside a C# component.<\/p>\n
Lists are a special construct that needs to be declared with a sentence you should get familiar to.<\/p>\n
List<double> myList = new List<double>();<\/pre>\n
We must precede our variable name with the words “List<dataType>” and then assign a “new” empty list by calling the function “List<double>()”. Whenever you see a statement with empty parenthesis like .ToString() you are dealing with a function (called methods in C# jargon).<\/p>\n
Let’s see lists in action:<\/p>\n
private void RunScript(ref object A, ref object B, ref object C)\r\n  {\r\n    \/\/declare a new list\r\n    List<int> myList = new List<int>();\r\n\r\n    \/\/fill the list with Fibonacci series\r\n    myList.Add(1);\r\n    myList.Add(1);\r\n    myList.Add(2);\r\n    myList.Add(3);\r\n    myList.Add(5);\r\n    myList.Add(8);\r\n    myList.Add(13);\r\n\r\n    \/\/output myList through A\r\n    A = myList;\r\n\r\n    \/\/create a new list copying the contents of myList\r\n    List<int> myReversedList = new List<int>(myList);\r\n\r\n    \/\/use the Reverse Method to find the reversed version of the list\r\n    myReversedList.Reverse();\r\n\r\n    \/\/output the second list through B\r\n    B = myReversedList;\r\n\r\n    \/\/retrieve the third element in the list\r\n    C = myList[2];\r\n\r\n  }<\/pre>\n
We interact with List mainly through methods and properties:<\/p>\n