diff options
Diffstat (limited to 'src/FunctionRef.h')
| -rw-r--r-- | src/FunctionRef.h | 37 |
1 files changed, 31 insertions, 6 deletions
diff --git a/src/FunctionRef.h b/src/FunctionRef.h index 8215fd0db..753d540a7 100644 --- a/src/FunctionRef.h +++ b/src/FunctionRef.h @@ -6,17 +6,42 @@ template <class Signature> class cFunctionRef; /** A light-weight, type-erased reference to a function object. -This is similar to a std::function but doesn't copy the function object -which means that mutable function objects will be modified for the caller -but would not be if using a std::function (See #3990 for implications of this). -A cFunctionRef has no empty state but is non-owning and so is safe to call -as long as the referred object is still alive. */ + +### Usage + +`cFunctionRef` is used whenever you call a normal function with a lambda. e.g. +one of the `cWorld::DoWith` functions, + + m_World->DoWithChunkAt(BlockPos, [](cChunk & a_Chunk) -> bool + { + ... + } + ); + +It looks like you're calling it with a lambda but that would require +`DoWithChunkAt` to be a template. The function is really being called with +`cFunctionRef<bool(cChunk&)>` which is constructed from the lambda via a +templated constructor. This gives you a generic pointer to the lambda which +doesn't depend on the type of the function object it references. + +### Notes + +- This is similar to a `std::function` but doesn't copy the function object. +This means that mutable function objects will be modified for the caller but +would not be if using a `std::function` (See #3990 for implications of this). + +- A `cFunctionRef` has no empty state but is non-owning and so is safe to call as +long as the referred object is still alive. */ template <class Ret, class... Args> class cFunctionRef<Ret(Args...)> { public: /** Construct from a function object. */ - template <class FunctionObject> + template <class FunctionObject, + typename std::enable_if< // Don't disable the default copy constructor + !std::is_same<typename std::decay<FunctionObject>::type, cFunctionRef>::value, + int>::type = 0 + > cFunctionRef(FunctionObject && a_FunctionObject) { // Store an opaque reference to the object. |