List Collection (PRIM_LCOL)
Sequential collection of objects accessible via an index
Ancestors - Collection (PRIM_COLL)Object (PRIM_OBJT)
Details
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.
Examples
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) ... Endfor
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))
Endroutine
Properties
| 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) |
Events
| 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 |
Methods
| Name | Description |
|---|---|
| Append | Add the components in the supplied collection to the end
OtherList |
| 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
Result |
| CreateIterator | CreateIterator method creates an iterator component that enables iteration through the collection
Result |
| Insert | Insert adds an item move continuing
Item |
| 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
Item |
| InsertLast | InsertLast adds an item in the end of the collection
Item |
| 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
Result |
| RemoveLast | Remove the last item from the collection
Result |
| ReplaceAt | Replace the instance at the specified position with a different object
Result, Item, Index |
See also
LANSA Version 15, April 2020