C++ iterator to access repeated elements.

[Alex Shaver]

(proto3)

Suppose I have some message with a repeated submessage element; especially given c++11's for range operator and other iterator-type algorithms, it feels like there should be iterator access to the submessages, beyond just the 'index' based approach.

I may be missing the fact that it does exist somewhere (the c++ documentation isn't up to date, really), or that there's other c++ limitations (these submessages are stored in some way that iterator access is prohibitively difficult/impossible). Otherwise, it definitely seems like an important element in the modern c++ styles.

[Feng Xiao]

Suppose you have the following proto definition:

message Foo {

  repeated Foo children = 1;

}

You should be able to write code like:

Foo foo = ...;

for (const Foo& child : foo.children()) {

  ...

}

 

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[Alex Shaver]

Ah, that's what I missed. The 'children' element is a 'RepeatedField' type which has the associated iterators. Thanks for the help.

[Alex Shaver]

Edit: just as a for instance:

suppose:
in proto file:

message Foo{
  repeated double values = 1;
}

in .cpp:

Foo protobuf;
protobuf.add_values(1.23);
protobuf.add_values(3.45);
protobuf.add_values(6.78);
std::vector<double> outVector{0,0,0};
std::transform(protobuf.values().cbegin(), protobuf.values().cend(), outVector.begin(), [](const double& in){return in + 1.5;});
std::vector<double> expectedVector{2.73, 4.95, 8.28};
ASSERT_EQ(expectedVector, outVector);

will be a successful test.