Menu
I have an integer field in a ClientDataSet and I need to compare to some values, something like this:
I can use const
const
mvValue1 = 1;
mvValue2 = 2;
if ClientDataSet_Field.AsInteger = mvValue1 then
or enums
TMyValues = (mvValue1 = 1, mvValue2 = 2);
if ClientDataSet_Field.AsInteger = Integer(mvValue1) then
or class const
TMyValue = class
const
Value1 = 1;
Value2 = 2;
end;
if ClientDataSet_Field.AsInteger = TMyValues.Value1 then
I like the class const approach but it seems that is not the delphi way, So I want to know what do you think
857
Solution 1. No, enum is a type that defines named values, a constant variable or value can be any type. You use an enum variable to hold a value of the enum type, you use a const to define a variable that cannot change and whose value is known at compile time.
A const parameter clearly tells the reader that the subroutine does not change the parameter's value. This improves the readability and clarity of the code. The compiler enforces the restriction. If you accidentally try to assign a new value to a const parameter, the compiler issues an error message.
Declaration:
type
TMyValues = class
type TMyEnum = (myValue1, myValue2, myValue3, myValue4);
const MyStrVals: array [TMyEnum] of string =
('One', 'Two', 'Three', 'Four');
const MyIntVals: array [TMyEnum] of integer =
(1, 2, 3, 4);
end;
Usage:
if ClientDataSet_Field.AsInteger = TMyValues.MyIntVals[myValue1] then
A cast would generally be my last choice.
126
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
