[fpc-pascal] same routine with different parameters?

Sven Barth pascaldragon at googlemail.com
Wed Oct 30 10:20:41 CET 2013

Am 29.10.2013 19:35, schrieb Mark Morgan Lloyd:
> waldo kitty wrote:
>> question: in simple language, how can i have a routine with differing 
>> parameters like some routines in FPC and Lazarus do? i've never 
>> attempted this before and it is completely alien to my experience but 
>> i do use the functionality quite a lot with existing routines...
>> description: i have a class object with an internal routine that i 
>> want to be able to pass no or different parameters to.
>> example:  procedure MyObject.MyRoutine;
>>           procedure MyObject.MyRoutine(VarA : SomeType);
>>           procedure MyObject.MyRoutine(VarA : string; VarB: integer);
>> at one point, the first instance would be used... at another point 
>> one of the other instances would be used with the only difference 
>> being the parameters that are passed or not... i know that i would 
>> have individual instances with the necessary header and code for 
>> each... i just don't know if there is anything else special that 
>> needs to be done or if it can be done with an internal class object 
>> routine..
> Just give it a whirl as you've shown, I think you've got it right. 
> Another useful variant is giving *the* *last* parameter an optional 
> value, which will allow you to omit the parameter:
> procedure MyObject.MyRoutine(const VarA : string; VarB: integer= -1);
Default paremeters can be used for more than the last parameter. There 
is however the following caveat: if you have e.g. a function with three 
parameters and the last two have default values, but you now have a call 
where you're fine with the default value of the second (overall) 
parameter, but not with that of the third you'll nevertheless have to 
specify the second parameter.


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