set numerci_range and read numeric_range

[Shahab Nassiri]

Hi

I want to set numeric_range on protobuf field and read the defined numeric_range in runtime. I use the file descriptor and field descriptor for this goal.

But i have a problem. I don't want to hard code the name of class variable.

I express one example about this. I define a day field in proto file and set numeric_range on it as following.

message Person{

      int32 day  = 1; [range_min = 5; range_max = 10]

}

now, I want to read the defined numeric_range in runtime.

for this goal, i must determine the variable name as hard code.

is there any way for determining the variable as string?

thank you

[Adam Cozzette]

You can reference Person::kDayFieldNumber to get the field number, and then look up the field descriptor with something like Person::descriptor()->FindFieldByNumber(Person::kDayFieldNumber).

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[Shahab Nassiri]

I want to access to field by the string. Your answer is by the class name. I use this solution at now.

[Michael Ngarimu]

From any Message you can call GetReflection(). 

From the Reflection call ListFields().

FieldDescriptor has a variety of “name” attributes that are available as strings against which to compare.

FieldDescriptor also has FieldOptions. I have not used FieldOptions for numeric_range but the documentation suggests that FieldOptions supports the options enclosed in []. https://protobuf.dev/reference/cpp/api-docs/google.protobuf.descriptor/#FieldDescriptor.options.details