Using object arrays

Object arrays reference a collection of input or output objects from an analysis step. You can access objects of the collection with an index. The group of found model occurrences in the ModelFinder step is an example of such a collection, as are results from the BlobAnalysis step, the Measurement step, and the PatternMatching step. Object arrays can prove useful to process such information. For example, you can use object array variables to compare the results of an analysis step against an expected set of values, such as comparing the Area of the blobs found against a set of valid areas.

Object array variables

Object array variables are read-only array variables that can only reference the results of an analysis step. Any analysis step that outputs an indexed collection of results can be referenced with an object array variable.

For example, after running a BlobAnalysis step, you can use an object array variable to reference the data for each blob found (BlobAnalysis.BlobFound(index)). The properties of that data can be accessed by expressions, such as:

SELECT(Blob_Results.BlobFound, Item.Area), which uses the SELECT array function to return the Area of each blob found in Blob_Results, which is an object array variable that references a BlobAnalysis step's results.
Blob_Results.BlobFound(1).Area, which returns the Area of only the first blob in the Blob_Results object array.

For information about accessing the results of a specific analysis step, see that step's accessing results section, such as the Accessing BlobAnalysis step results section in Chapter 3: BlobAnalysis step.

Sub-arrays

Some analysis steps can output an indexed collection whose elements are themselves indexed collections. Sub-arrays refer to these additional layers of collections. For example, in a StringReader step, you can reference the collection of strings read for a particular string model, using the expression: StringReader.StringModels.StringModel.StringsRead. Each string read also consists of an indexed collection of characters. Since arrays in Matrox Design Assistant are one-dimensional, to use an object array to reference the collection of characters in a particular string, you would use the expression: StringReader.StringModels.StringModel.StringsRead.Characters.

The FLATTEN array function is useful when you have a collection of objects inside an element of another collection, and you want to reference the properties of both the parent collection and the child collection within the same expression. The function uses the SourceArray parameter to reference the parent collection and the SubArray parameter to reference the child collection. Using the SubIndex, SubItem, and SubItemCount keywords lets you point to the properties of the child collection.

For more information, see the Array functions section later in this chapter.