>I want to create an object and need this object keep an array of other objects. How can I do it?
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>I mean, how to create a behavior similar to that in pageframes, containers, forms or so, that keeps a collection of objects inside a single object? Even more, how could it keep track of the number of elements?

Use property-array and ALEN(thisform.amyarray) will return the number of elements. Any time you add/remove new member, you will redimension this array.