use of generic types and specialize
lazarus / 21-General

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SA.Blackmon · 2021-01-12 00:12

I am working on learning more about Lazarus and so far am doing
reasonably well (my own estimate.)

The idea of generic types in "https://freepascal.org/docs-
html/ref/refse52,3,4.html" is something I believe I can incorporate
profitably into my code.

That is, when I get it to work.

I have some code where I copied from the above url's and it mostly
does not compile.

Please see the zip attachment for the project with embedded comments
that specify the compiler errors. I suspicion that  it has to do with
compiler directives.

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jamie · 2021-01-12 00:24

Nice, Website not found. The Electrons over the horizon must be
getting reflected!

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trev · 2021-01-12 02:55

It's a composite URL

Start at https://freepascal.org/docs-html/ref/refse52.html

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PascalDragon · 2021-01-12 08:02

Quote from: SA.Blackmon on January 12, 2021, 01:12:52 amI have some
code where I copied from the above url's and it mostly does not
compile.

Please see the zip attachment for the project with embedded comments
that specify the compiler errors. I suspicion that  it has to do with
compiler directives.

You need to declare your TList<> and TObjectList<> before they are
used (thus before line 29). Or alternatively use those from the unit
Generics.Collections (of course if you only implemented them to learn,
please continue  ).

Generic functions/procedures/methods (aka “routines”) is mostly useful
if you have some simple utility functions that you want to be
typesafe. Or you want to avoid to write X overloads that are all
essentially doing the same for different types.

In line 115 (your call to compare) you pass a number to a function
that takes either a TComponent or a TDiffRecord descendant. You need
to use two different elements of your list to compare them, not an
element and a number.