4D v19
collection.copy( )
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- collection.copy( )
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collection.copy( )
The collection.copy( ) method returns a deep copy of the collection instance. Deep copy means that objects or collections within the original collection are duplicated and do not share any reference with the returned collection.
Note: This method does not modify the original collection.
If passed, the option parameter can contain one of the following constants (or both):
| option | Description |
| ck resolve pointers | If the original collection contains pointer type values, by default the copy also contains the pointers. However, you can resolve pointers when copying by passing the ck resolve pointers. In this case, each pointer present in the collection is evaluated when copying and its dereferenced value is used. |
| ck shared | By default, copy( ) returns a regular (not shared) collection, even if the command is applied to a shared collection. Pass the ck shared constant to create a shared collection. In this case, you can use the groupWith parameter to associate the shared collection with another collection or object (see below). |
The groupWith parameter allows you to designate a collection or an object with which the resulting collection should be associated.
We want to copy the $lastnames regular (non shared) collection into the $sharedObject shared object. To do this, we must create a shared copy of the collection ($sharedLastnames).
C_OBJECT($sharedObject)
C_COLLECTION($lastnames;$sharedLastnames)
C_TEXT($text)
$sharedObject:=New shared object
$text:=Document to text(Get 4D folder(Current resources folder)+"lastnames.txt")
$lastnames:=JSON Parse($text) //$lastnames is a regular collection
$sharedLastnames:=$lastnames.copy(ck shared) //$sharedLastnames is a shared collection
//Now we can put $sharedLastnames into $sharedObject
Use($sharedObject)
$sharedObject.lastnames:=$sharedLastnames
End useWe want to combine $sharedColl1 and $sharedColl2. Since they belong to different shared groups, a direct combination would result in an error. Therefore, we must make a shared copy of $sharedColl1 and designate $sharedColl2 as a shared group for the copy.
C_COLLECTION($sharedColl1;$sharedColl2;$copyColl)
$sharedColl1:=New shared collection(New shared object("lastname";"Smith"))
$sharedColl2:=New shared collection(New shared object("lastname";"Brown"))
//$copyColl belongs to the same shared group as $sharedColl2
$copyColl:=$sharedColl1.copy(ck shared;$sharedColl2)
Use($sharedColl2)
$sharedColl2.combine($copyColl)
End useWe have a regular collection ($lastnames) and we want to put it in the Storage of the application. To do this, we must create a shared copy beforehand ($sharedLastnames).
C_COLLECTION($lastnames;$sharedLastnames)
C_TEXT($text)
$text:=Document to text(Get 4D folder(Current resources folder)+"lastnames.txt")
$lastnames:=JSON Parse($text) //$lastnames is a regular collection
$sharedLastnames:=$lastnames.copy(ck shared) // shared copy
Use(Storage)
Storage.lastnames:=$sharedLastnames
End useThis example illustrates the use of the ck resolve pointers option:
C_COLLECTION($col)
C_POINTER($p)
$p:=->$what
$col:=New collection
$col.push(New object("alpha";"Hello";"num";1))
$col.push(New object("beta";"You";"what";$p))
$col2:=$col.copy()
$col2[1].beta:="World!"
ALERT($col[0].alpha+" "+$col2[1].beta) //displays "Hello World!"
$what:="You!"
$col3:=$col2.copy(ck resolve pointers)
ALERT($col3[0].alpha+" "+$col3[1].what) //displays "Hello You!"
Product: 4D
Theme: Collections
4D Language Reference ( 4D v19)
4D Language Reference ( 4D v19.1)
