PragmaTwice opened a new pull request, #768:
URL: https://github.com/apache/incubator-kvrocks/pull/768
In kvrocks we use a style like `Status process(input..., T* output)` to
handle errors. It works well, but in C++ we can do better via constructing
type-safe union types.
In this PR, we propose a new class template `StatusOr<T>`, which contains
either a value typed T or a status. Here is a simple example:
```c++
StatusOr<std::string> hello(std::string x) {
if (x.size() > 10) {
return {Status::NotOK, "string too long"};
}
return x + " hello";
};
StatusOr<std::string> hi(std::string x) {
if (x.size() < 5) {
return {Status::NotOK, "string too short"};
}
auto res = f(x);
if (!res) return res;
return "hi " + *res;
};
assert(*hi("twice") == "hi twice hello");
auto short = hi("x");
assert(!short && short.Msg() == "string too short");
auto long= hi("xxxxxxxxxxx");
assert(!long && long.Msg() == "string too long");
```
We maximize the use of move semantics in C++ to eliminate redundant copies
and optimize the storage, so that developers do not need to worry too much
about its performance when using it.
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