Why can't I New() a GROUP and what workaround/alternatives are there?

questions
1

It seems strange to me that you cannot New() a GROUP in Clarion. I seem to recall that there is an actual reason for this but I cannot find a reference describing that reason and now I am curious.

Possible alternatives?

Using a QUEUE instead, but just using it for the structure:

myFakeGroup_Type     GROUP,TYPE
someField              LONG
                     END
myFakeGroup          &myFakeGroup_Type
  CODE

  myFakeGroup &= New(myFakeGroup_Type)

  myFakeGroup.someField = 12
  Stop(myFakeGroup.someField)
  Dispose(myFakeGroup)

Using a STRING + GROUP:

myGroup_Type         GROUP,TYPE
someField              LONG
                     END
myGroupString        &STRING
myGroup              &myGroup_Type
  CODE

  myGroupString &= New(STRING(Size(myGroup_Type)))
  myGroup &= Address(myGroupString)

  myGroup.someField = 12
  Stop(myGroup.someField)
  Dispose(myGroupString)

Note: With that approach I think you need to be careful about the size if you have Dim() variables in your GROUP.

1 Like
2

You can use a CLASS as your GROUP
I believe it uses another 4 or 8 bytes, but for most use cases that doesn’t matter.

You could even declare the class as

MyGroupClass  CLASS(myFakeGroup_Type),TYPE
              END

One problem with using classes vs. groups
Is when you want to copy all values like this

GroupClassA  &MyGroupClass
GroupClassB  &MyGroupClass
    CODE
   GroupClassA &= NEW MyGroupClass
   GroupClassB &= NEW MyGroupClass
   GroupClassA.SomeField = 47
  
   GroupClassB = GroupClassA  !<--- UNUSUAL TYPE CONVERSION

above is a normal syntax (for real groups) to copy all fields
however for classes, this will generate a warning UNUSUAL TYPE CONVERSION

When I requested some sort of fix to the compiler
Alexey just suggested that I use a memcpy to avoid the warning