[fpc-pascal] Coercing record fields together

[Ryan Joseph]

Could I do some RTL magic on a record to loop over its fields and set them to another record by name? In the example below I want to set all the fields in TRecA to matching named fields in TRecB. Just curious if we can do this automatically using RTL.

type
TRecA = record
a: string;
b: string;
end;

type
TRecB = record
a: string;
b: string;
c: integer;
d: integer;
end;


for field in recA.GetFields do
recB.GetFieldByName(field.name).value := field.value


Regards,
Ryan Joseph

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[DaWorm]

Just because someone is bound to suggest it, might as well be me.

type
TRecA = record
a: string;
b: string;
end;

type
TRecB = record
A: TRecA;
c: integer;
d: integer;
end;

RecB.A := RecA;

Jeff

Post by Ryan Joseph
Could I do some RTL magic on a record to loop over its fields and set them
to another record by name? In the example below I want to set all the
fields in TRecA to matching named fields in TRecB. Just curious if we can
do this automatically using RTL.
type
TRecA = record
a: string;
b: string;
end;
type
TRecB = record
a: string;
b: string;
c: integer;
d: integer;
end;
for field in recA.GetFields do
recB.GetFieldByName(field.name).value := field.value
Regards,
Ryan Joseph
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[gabor]

Hi.
Probably can be done with RTTI (1), enumerators (2) and generics (3)
together.

1. https://stackoverflow.com/questions/27803383/fpc-rtti-on-records
2. http://wiki.freepascal.org/for-in_loop#Traversing_container
3. http://wiki.freepascal.org/Generics

Michał.

Post by Ryan Joseph
Could I do some RTL magic on a record to loop over its fields and set them to another record by name? In the example below I want to set all the fields in TRecA to matching named fields in TRecB. Just curious if we can do this automatically using RTL.
type
TRecA = record
a: string;
b: string;
end;
type
TRecB = record
a: string;
b: string;
c: integer;
d: integer;
end;
for field in recA.GetFields do
recB.GetFieldByName(field.name).value := field.value
Regards,
Ryan Joseph
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[Ryan Joseph]

Hi.
Probably can be done with RTTI (1), enumerators (2) and generics (3) together.
1. https://stackoverflow.com/questions/27803383/fpc-rtti-on-records
2. http://wiki.freepascal.org/for-in_loop#Traversing_container
3. http://wiki.freepascal.org/Generics
Michał.

Thanks for the tips but ouch that looks complicated, maybe more trouble than it’s worth.

Regards,
Ryan Joseph

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[Ralf Quint]

Post by Ryan Joseph
Could I do some RTL magic on a record to loop over its fields and set them to another record by name? In the example below I want to set all the fields in TRecA to matching named fields in TRecB. Just curious if we can do this automatically using RTL.
type
TRecA = record
a: string;
b: string;
end;
type
TRecB = record
a: string;
b: string;
c: integer;
d: integer;
end;
for field in recA.GetFields do
recB.GetFieldByName(field.name).value := field.value

If you make sure that any variable of tRecB is declared first, you can use

Var RecB : tRecB;
       RecA : tRedA ABSOLUTE RecB;

Quite obviously, it doesn't work the other way around as tRecB is larger
than tRecA...

Ralf

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[Martin]

Post by Ryan Joseph
Could I do some RTL magic on a record to loop over its fields and set them to another record by name? In the example below I want to set all the fields in TRecA to matching named fields in TRecB. Just curious if we can do this automatically using RTL.
type
TRecA = record
a: string;
b: string;
end;
type
TRecB = record
a: string;
b: string;
c: integer;
d: integer;
end;
for field in recA.GetFields do
recB.GetFieldByName(field.name).value := field.value

I don't know about the loop, but if records with inheritance would help,
you could do:

type

TRecA = object
a: string;
b: string;
end;

TRecB = object(TRecA)
c: integer;
d: integer;
end;

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