Given an Ada protected type:
protected type A is
procedure Foo;
...
private
M : Map;
...
end A;
How would you开发者_Python百科 implement or emulate a Finalize procedure that is called when the protected object is finalized?
Basically I need to do some house keeping using the private members of the protected type (iterating over some map and so on).
Wrap the private members that have a part in the finalization in one or more records derived from Ada.Finalization.Controlled or Limited_Controlled. When the protected object is finalized, those private members will be correspondingly finalized as well.
Here's a quick, working(!) example:
with Text_IO; use Text_IO;
with Ada.Finalization;
with Ada.Containers.Ordered_Maps;
with Ada.Unchecked_Deallocation;
procedure Protected_Final is
Instance_Counter : Natural := 1;
package Int_Map is new Ada.Containers.Ordered_Maps (Integer, Integer);
subtype Map is Int_Map.Map;
type Map_Wrapper is new Ada.Finalization.Controlled with record
ID : Natural;
M : Map;
end record;
overriding procedure Initialize(Item : in out Map_Wrapper);
overriding procedure Finalize(Item : in out Map_Wrapper);
procedure Initialize(Item : in out Map_Wrapper) is
begin
Item.ID := Instance_Counter;
Instance_Counter := Instance_Counter + 1;
Put_Line("Initialize the Map part as instance" & Natural'Image(Item.ID));
end Initialize;
procedure Finalize(Item : in out Map_Wrapper) is
begin
Put_Line("Clean up the Map stuff for instance" & Natural'Image(Item.ID));
end Finalize;
protected type A is
procedure Foo;
private
M : Map_Wrapper;
end A;
protected body A is
procedure Foo is
begin
null;
end Foo;
end A;
Test_Item : A;
type A_Handle is access A;
procedure Free is new Ada.Unchecked_Deallocation(A, A_Handle);
Test_Item_Handle : A_Handle;
begin
Test_Item_Handle := new A;
Free(Test_Item_Handle);
end Protected_Final;
Running this I get:
C:\sandbox\protected_final
Initialize the Map part as instance 1
Initialize the Map part as instance 2
Clean up the Map stuff for instance 2
Clean up the Map stuff for instance 1
[2011-03-04 08:37:29] process terminated successfully (elapsed time: 00.21s)
The "outer" Initialize/Cleanup messages come are a result of the statically declared Test_Item instance, while the inner pair are from the dynamically allocated and deallocated Test_Item_Handle.
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