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In RAII, holding a resource is a class invariant, and is tied to object lifetime. Resource allocation (or acquisition) is done during object creation (specifically initialization), by the constructor, while resource deallocation (release) is done during object destruction (specifically finalization), by the destructor. In other words, resource ...
This is called the Resource Acquisition Is Initialization (RAII) idiom. Resources are acquired during initialization, and released during finalization. In languages with non-deterministic lifetime objects (i.e. garbage collected), the management of memory is generally kept separate from management of other resources.
Normally, when an object is created dynamically, an allocation function is invoked in such a way that it will both allocate memory for the object, and initialize the object within the newly allocated memory. The placement syntax allows the programmer to supply additional arguments to the allocation function.
The C++ standard library instead provides a dynamic array (collection) that can be extended or reduced in its std::vector template class. The C++ standard does not specify any relation between new / delete and the C memory allocation routines, but new and delete are typically implemented as wrappers around malloc and free. [6]
This feature is often used to manage resource allocation and deallocation, like opening and then automatically closing files or freeing up memory, called Resource Acquisition Is Initialization (RAII). Since C++11, C++ allows variables to be declared with the auto type specifier, [3] but this means that the variable's type is inferred, and does ...
Object pooling requires resources – memory and possibly other resources, such as network sockets, and thus it is preferable that the number of instances in use at any one time is low, but this is not required. The pooled object is obtained in predictable time when creation of the new objects (especially over network) may take variable time.
Local variables are destroyed when the local block or function that they are declared in is closed. C++ destructors for local variables are called at the end of the object lifetime, allowing a discipline for automatic resource management termed RAII, which is widely used in C++. Member variables are created when the parent object is created.
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed. It is a kind of lazy evaluation that refers specifically to the instantiation of objects or other resources.