Re: [fpc-pascal] Unrelated type helpers with the same members? Implement an interface with a type helper?
On Thu, 22 Dec 2022, Andrew Haines via fpc-pascal wrote: Hi what I want to do is similar to this question here: https://en.delphipraxis.net/topic/423-rtti-determine-record-helper-type-for-a-base-type/ I am going to create multiple type helpers for enums and I would like to look up the helper and use common methods AsString AsOrdinal to get/set the values. I am recieving them as json that I dont have control over. I am using typeinfo to fill in all the properties but I would like to convert the strings I am receiving to the enum values semi-automatically. LString := 'STATUS'; LHelper := GetHelper(LPropInfo^.PropType); // enum proptype Since there can be multiple type helpers for a type, this will never be possible. At best you would get a list. But I don't think there is even a list of type helpers per type. Sven will need to confirm. In your case, I would simply register a function that does this for each known enum type. Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Unrelated type helpers with the same members? Implement an interface with a type helper?
So, I came up with a solution using Custom Attributes.
I can declare this:
[TEnumAttr('YES', 'NO', 'COULD_BE')]
TMyEnum = (meYes, meNo, meCouldBe);
and at runtime look for the TEnumAttr attribute and use that.
TEnumAttr = class(TCustomAttribute)
protected
FValues: TStringArray;
FTypeName: String;
public
class function FromType(ATypeInfo: PTypeInfo): TEnumAttr;
constructor Create(Val1: String);
constructor Create(Val1, Val2: String);
etc
Maybe this can help someone else with a similar use case.
Regards,
Andrew Haines
On 12/22/22 8:40 PM, Andrew Haines via fpc-pascal wrote:
Hi what I want to do is similar to this question here:
https://en.delphipraxis.net/topic/423-rtti-determine-record-helper-type-for-a-base-type/
I am going to create multiple type helpers for enums and I would like
to look up the helper and use common methods AsString AsOrdinal to
get/set the values. I am recieving them as json that I dont have
control over. I am using typeinfo to fill in all the properties but I
would like to convert the strings I am receiving to the enum values
semi-automatically.
LString := 'STATUS';
LHelper := GetHelper(LPropInfo^.PropType); // enum proptype
LToStringInterface := LHelper as IToStringInterface;
SetOrdProp(LObject, 'propname', LToStringInterface.OrdValue(LString);
Something like that. I'm not sure if it's even possible to find the
helper type with typeinfo.
Thanks for your suggestions :)
Regards,
Andrew
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[fpc-pascal] Unrelated type helpers with the same members? Implement an interface with a type helper?
Hi what I want to do is similar to this question here: https://en.delphipraxis.net/topic/423-rtti-determine-record-helper-type-for-a-base-type/ I am going to create multiple type helpers for enums and I would like to look up the helper and use common methods AsString AsOrdinal to get/set the values. I am recieving them as json that I dont have control over. I am using typeinfo to fill in all the properties but I would like to convert the strings I am receiving to the enum values semi-automatically. LString := 'STATUS'; LHelper := GetHelper(LPropInfo^.PropType); // enum proptype LToStringInterface := LHelper as IToStringInterface; SetOrdProp(LObject, 'propname', LToStringInterface.OrdValue(LString); Something like that. I'm not sure if it's even possible to find the helper type with typeinfo. Thanks for your suggestions :) Regards, Andrew ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
