2015-06-15 17:14 GMT+02:00 Matthieu Lacaton <matthieu.lacaton@gmail.com>:
Hello everyone,
I have a nested struct, let's say "struct1" which contains "struct2" which contains an int field named "field".
When I try to update the field from struct 1 directly I can't. What I mean is if I do : "struct1 struct2 field: 4" for instance, the value in field is not updated. Even if I inspect "struct1 struct2" and I manually set the "field variable by doing : "self field: 4" then if I go back to my struct1 and do "self struct2 field" the value has not been updated. So basically the only way I have to update a field in a nested structure is to recreate the second struct entirely : "struct1 struct2: (Struct2 new field: 4)" and now it works.
It seems odd because in C you can do "struct1.struct2.field = 4;" and it works fine.
yes, self struct2 will create a copy of the struct2 and any change to struct2 value only applies to this copy.
You can reproduce this with the NBTestNestedStructure class from NativeBoost itself :
| myStruct |
myStruct := (NBTestNestedStructure new oneByte: (NBTestStructure1byte new field: 1)). Transcript show: myStruct oneByte field; cr. myStruct oneByte field: 4. Transcript show: myStruct oneByte field; cr. myStruct oneByte: (NBTestStructure1byte new field: 4). Transcript show: myStruct oneByte field; cr.
For me the Transcript shows 1 1 4 whereas in my opinion it should show 1 4 4.
So am I doing something wrong or is this some kind of a bug ?
I am not sure, I think there is no other way to handle this kind of nested structures. Are you bound to exactly this structure? If you can define the structure, you can use a nested structure that uses pointers instead of values: NBTestNestedStructure2>> fieldsDesc ^ #( NBTestStructure1byte* oneByte; int otherField ) Now you can create and access the innerstructure like this myStruct := (NBTestNestedStructure2 new oneByte: (NBTestStructure1byte externalNew field: 1)). myStruct oneByte field. " -> 1 " myStruct oneByte field: 4. myStruct oneByte field. " -> 4 " Whereas I don't know if the external memory is freed.
Thanks,
Matthieu