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Back to article list Search Articles Add Comment Printer friendly Direct link Par2: PRE() on Queues and referring to queue fields 1999-06-20 -- Carl Barnes In CW20 something called Field Qualification was added to the Clarion Language but
not the IDE. See the LRM for some info. It replaces the use of Prefixes by using the
higher level name of the GROUP or QUEUE plus a Dot plus the field name. This is also
called Dot Syntax. This is the prefered way to access structures now.
E.g. in this structure:
FilesQ QUEUE
Name STRING(20)
Date LONG
END
To use the Name variable you type FileQ.Name. Trouble is that previous to Cw20 you
could just use "Name". To solve this syntax problem they changed the rules a bit, you
have to add a blank prefix, i.e. PRE(). With PRE() you can still call it "Name" and also
call it FileQ.Name. But the empty PRE() is being Deprecated, i.e. it's a legacy.
Enter another problem, the IDE does not support Field Qualification and it does not
support prefixes. Thru the Data button you can only do PRE() or more correct, you
cannot enter a prefix. Oddly this was supported in 3.0 DOS.
So you need to make unique field names, sorry but thats the way it is. It is very livable.
I tend to add a Prefix to each field name so I would enter the above group under Data
as:
FilesQ QUEUE
FQ:Name STRING(20)
FQ:Date LONG
END
Starting in C5B they have added PRE() to the Data button IDE. And they are working on
doing Dot.syntax thru the IDE. So the future is good. C5b should ship shortly.
To summarrize:
1. Prior to C5B thru the IDE all GROUP and QUEUE use PRE() so you must have
unique field names. It's not that tuff.
2. When you hand code your QUEUE in the Data embeds then if you leave off
PRE() you must use QueueName.Fieldname dot.syntax.
3. When you hand code your QUEUE in the Data embeds and you use PRE(XXX) you
can use XXX:FieldName or QueueName.Fieldname dot.syntax.
Your #2 problem of wanting to create a Queue thru the DATA button without a
PRE() is a good one, the reason you cannot is that the IDE does not support
dot.syntax. So make your prefix name the same as your Queue name.
Your #3 problem I just checked in C5Bv the lastest alpha build and I was
allowed to create two Queues with different prefixes and the same field
names. Here's what I did:
Q1 QUEUE,PRE(Q1)
NAME string(20)
.
Q2 QUEUE,PRE(Q2)
NAME string(20)
.
One possible bug you should be aware of is that Reference variables and
Reference assignments do not support the blank PRE(). You must use
field.qualification. The compiler will take some of them but they will not
work. So if you have a group
MyG GROUP,PRE()
MG:WinRef &Window
END
Even if MG:WinRef is unique you must use MyGroup.MG:WinRef &= Window
Today is November 21, 2024, 7:19 am This article has been viewed 35295 times.
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