blocking
Adds a new object to the given collection in a synchronous way based on the provided CreateProjection. It blocks the current thread and returns the generated UID. It adds an object with a State.TO_POST, which will be uploaded to the server in the next upload. Important: this is a blocking method and it should not be executed in the main thread. Consider the asynchronous version .rxAdd.
Return
the UID
Parameters
o
the CreateProjection of the object to add