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// might not use the 'bslma' allocator protocol.
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//
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// First, we define a wrapper class that holds an object and a functor and
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// calls the functor (called the listener) each time the wrapped object is
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// changed. We store the object directly as a member variable, instead of
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// using an uninitialized buffer, to avoid a separate construction step:
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//..
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template <class TYPE, class FUNC>
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class MyTriggeredWrapper {
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// This class is a wrapper around an object of the specified 'TYPE'
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// that triggers a call to an object, called the "listener", of the
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// specified 'FUNC' invocable type whenever the wrapped object is
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// changed.
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// DATA
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TYPE d_value;
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FUNC d_listener;
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public:
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// CREATORS
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explicit MyTriggeredWrapper(const FUNC& f,
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bslma::Allocator *basicAllocator = 0);
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MyTriggeredWrapper(const TYPE& v,
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const FUNC& f,
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bslma::Allocator *basicAllocator = 0);
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// Create an object with the specified 'f' as the listener to be
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// called when a change is triggered. Optionally specify 'v' as
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// the wrapped value; otherwise the wrapped value is default
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// constructed. Optionally specify 'basicAllocator' to supply
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// memory; otherwise the current default allocator is used. If
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// 'TYPE' is not allocator aware, 'basicAllocator' is ignored.
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MyTriggeredWrapper(const MyTriggeredWrapper& original,
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bslma::Allocator *basicAllocator = 0);
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// Create a copy of the specified 'original'. Optionally specify
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// 'basicAllocator' to supply memory; otherwise the current
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// default allocator is used.
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~MyTriggeredWrapper()
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// Destroy the wrapped object and listener.
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{
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}
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// MANIPULATORS
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MyTriggeredWrapper& operator=(const TYPE& rhs);
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MyTriggeredWrapper& operator=(const MyTriggeredWrapper& rhs);
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// Assign the wrapped value to the value of the specified 'rhs',
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// invoke the listener with the new value, and return a reference
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// providing modifiable access to this object. Note that the
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// listener itself is not assigned.
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void setValue(const TYPE& value);
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// Set the wrapped value to the specified 'value' and invoke the
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// listener with the new value.
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// ACCESSORS
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const TYPE& value() const
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// Return a reference providing read-only access to the wrapped
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// value.
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{
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return d_value;
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}
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const FUNC& listener() const
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// Return a reference providing read-only access to the listener.
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{
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return d_listener;
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}
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};
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//..
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// Next, we define the constructors such that they initialize 'd_value' using
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// the specified allocator if and only if 'TYPE' accepts an allocator. The
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// 'bslma::ConstructionUtil::make' family of functions encapsulate all of the
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// metaprogramming that detects whether or not 'TYPE' uses an allocator and,
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// if so, which construction protocol it uses (allocator at the front or at
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// the back of the argument list), making all three constructors straight-
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// forward:
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//..
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template <class TYPE, class FUNC>
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MyTriggeredWrapper<TYPE, FUNC>::MyTriggeredWrapper(
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const FUNC& f,
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bslma::Allocator *basicAllocator)
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: d_value(bslma::ConstructionUtil::make<TYPE>(basicAllocator))
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, d_listener(f)
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{
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}
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template <class TYPE, class FUNC>
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MyTriggeredWrapper<TYPE, FUNC>::MyTriggeredWrapper(
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const TYPE& v,
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const FUNC& f,
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bslma::Allocator *basicAllocator)
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: d_value(bslma::ConstructionUtil::make<TYPE>(basicAllocator, v))
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, d_listener(f)
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{
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}
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template <class TYPE, class FUNC>
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MyTriggeredWrapper<TYPE, FUNC>::MyTriggeredWrapper(
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const MyTriggeredWrapper& other,
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