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Updated engine version Changed font settings for multiple terms Changed all mentions of NULL to null to reflect changes made to the engine. [CL 2622058 by Matthew Clark in Main branch]
55 lines
2.4 KiB
Plaintext
55 lines
2.4 KiB
Plaintext
Availability:Public
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Title:Shared References
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Crumbs:%ROOT%, Programming, Programming/UnrealArchitecture/SmartPointerLibrary
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Description:Smart pointer type that cannot be uninitialized or assigned null.
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Version: 4.9
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[TOC(start:2)]
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A **shared reference** is a non-nullable shared pointer. This means you cannot create an empty shared reference and you cannot assign null to a shared reference, which helps you write safer, cleaner code since you know it is safe to access the object. In fact, shared references do not even have an **IsValid()** method - like shared pointers do - since they are always valid. It is recommended to always use shared references instead of shared pointers when possible.
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If you need empty/nullable references, you should use [](Programming/UnrealArchitecture/SmartPointerLibrary/SharedPointer) instead.
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## Declaration and Initialization
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Shared references are always initialized with a valid object and cannot be declared without being initialized.
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An example of creating a new shared reference:
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// Create a shared reference to a new node
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TSharedRef<FTreeNode> NodeRef( new FTreeNode() );
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Attempting to declare a shared reference without initializing it or assigning null is never allowed:
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TSharedRef<UBool> EmptyBool; // Will not Compile!!
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## Shared Reference Usage
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For the most part, using a shared reference is just like using a shared pointer.
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// Create a shared reference to a new node
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TSharedRef<FTreeNode> NodeRef( new FTreeNode() );
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NodeRef->ListChildren();
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( *NodeRef ).ListChildren();
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const FTreeNode& NodeVar = NodeRef.Get();
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Again, the main difference is that you cannot set a shared pointer to null:
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TSharedRef<FTreeNode> Node = null; // Will not Compile!!
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### Pointer and Reference Conversion
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Shared references convert to shared pointers implicitly so it is always safe to make a pointer from a reference, i.e. you can assign a shared reference to a shared pointer or pass a shared reference to a method expecting a shared pointer.
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TSharedPtr<FTreeNode> SomeNodePtr = NodeRef;
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However, conversion from a pointer is potentially unsafe, and you are forced to explicitly perform the conversion using the **ToSharedRef()** function.
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// Explicitly reference a pointer. Will assert if the pointer is not valid!
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NodeRef = SomeNodePtr.ToSharedRef();
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[REGION:note]
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In a similar manner to the * operator with C++ pointers, using ToSharedRef() will assert if the object is not valid.
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[/REGION]
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