List Collection (PRIM_LCOL)

Sequential collection of objects accessible via an index

Ancestors - Collection (PRIM_COLL)Object (PRIM_OBJT)


List collections provide an ordered collection of components.
The features of the list component are positional in nature, in reference to a given index or to the beginning or end of the list. Indexing is always relative to 1.
List collections and Array collections are very similar in nature, the only real difference being the way they handle memory allocation in Windows.


Defining a list collection. This collection stores instances of a user defined customer data object.
Define_Com Class(#Prim_Lcol<#Customer>) Name(#Customers)
Collection items can be created by assigning them to an existing reference or creating a new one as below.
#Customers.Insert((*New #Customer))
Collection items can be accessed by their position in the collection.
#Customers<123>.CustomerName := #CustomerName
All collection items can be addressed as follows. Here, all the customers in the collection are having a property value incremented.
#Customers<>.CreditLimit += 1000
The FOR command can also be used to iterate over the collection contents. The items will be returned in the order they are stored in the collection.
For each(#Customer) in (#Customers)
To monitor for an event from any instance in the collection, <> can be appended to an EVTROUTINE. The COM_SENDER parameter will provide access to the instance firing the event.
In this example, a changed event on the customer instances is monitored.
Evtroutine Handling(#Customers<>.Changed) Com_Sender(#Sender)
   #Com_owner.AddEvent(("&1 changed").Substitute(#Sender.CustomerName))


Name Description
AllowsDuplicates AllowsDuplicates indicates whether the collection allows duplicates Inherited from Collection (PRIM_COLL)
Collects The class of object to be collected
ComponentClassName ComponentClassName is the name of the component's class. Inherited from Object (PRIM_OBJT)
ComponentMembers ComponentMembers provides access to all the member components of this component Inherited from Object (PRIM_OBJT)
ComponentPatternName ComponentPatternName is used to qualify the class of the component. Inherited from Object (PRIM_OBJT)
ComponentTag Generic space allowing a value to be stored for the instance Inherited from Object (PRIM_OBJT)
ComponentType ComponentType gives you access to the type information about the component Inherited from Object (PRIM_OBJT)
ComponentTypeName ComponentTypeName is the fully qualified name of the component's class. Inherited from Object (PRIM_OBJT)
First Reference to the first item in the collection
IndexOf IndexOf returns the index number of an item in a collection
IsEmpty IsEmpty indicates whether the collection contains any items. Inherited from Collection (PRIM_COLL)
IsOrdered IsOrdered indicates whether the collection is ordered. Inherited from Collection (PRIM_COLL)
Item Provides access to a particular item in a collection
ItemCount ItemCount is the number of items in a collection Inherited from Collection (PRIM_COLL)
Last Last is the Last item in a collection
LastIndexOf The LastIndexOf property searches the list looking for the last occurrences of a component.
Name Name identifies the component Inherited from Object (PRIM_OBJT)
Owner Owner owns this component Inherited from Object (PRIM_OBJT)
Parent The component instance to which this instance is attached. The visual container for a control or the collector of a set of child instances Inherited from Object (PRIM_OBJT)


Name Description
CreateInstance CreateInstance is signalled when an instance of a component is created Inherited from Object (PRIM_OBJT)
DestroyInstance DestroyInstance is signalled when an instance of a component is about to be destroyed Inherited from Object (PRIM_OBJT)
IsEqual Fired whenever the collection needs to compare two items
Object, Subject, Equal


Name Description
Append Add the components in the supplied collection to the end
CalculateHash CalculateHash calculates a hash value Inherited from Collection (PRIM_COLL)
Result, Value
Concatenate Combine two collections to create a new collection
Result, OtherList
Contains Does the supplied instance exist in the collection?
Result, Object
CreateAccessor CreateAccessor creates an accessor component that provides read-only access to the collection
CreateIterator CreateIterator method creates an iterator component that enables iteration through the collection
Insert Insert adds an item move continuing
InsertAfter InsertAfter adds an item to a collection after a specified position
Item, Index
InsertBefore InsertBefore adds an item to a collection before a specified item
Item, Index
InsertFirst InsertFirst adds an item in the beginning of the collection
InsertLast InsertLast adds an item in the end of the collection
OccurrencesOf Find the number of occurrences of an instance in the collection
Result, Object
Remove Remove method removes an item
Result, Object
RemoveAll RemoveAll removes all items in the collection
RemoveAt Removes the item at the specified position
Result, Index
RemoveFirst Remove the first item from the collection
RemoveLast Remove the last item from the collection
ReplaceAt Replace the instance at the specified position with a different object
Result, Item, Index

See also

All Component Classes

Technical Reference

LANSA Version 15, April 2020