winrt::observable_vector_base struct template (C++/WinRT)
A base class from which you can derive to implement your own custom observable vector. For more info, and code examples, see Collections with C++/WinRT.
Syntax
template <typename D, typename T>
struct observable_vector_base : vector_base<D, T>
Template parameters
typename D
Your derived type name.
typename T
The type of the elements in the observable_vector_base.
Requirements
Minimum supported SDK: Windows SDK version 10.0.17763.0 (Windows 10, version 1809)
Namespace: winrt
Header: %WindowsSdkDir%Include<WindowsTargetPlatformVersion>\cppwinrt\winrt\base.h (included by default)
Member functions
| Function | Description |
|---|---|
| observable_vector_base::Append function | Appends an element to the end of the observable_vector_base object. |
| observable_vector_base::Clear function | Removes all elements from the observable_vector_base object. |
| observable_vector_base::First function | Retrieves an IIterator representing the first element in the observable_vector_base object. |
| observable_vector_base::GetAt function | Retrieves the element at the specified index in the observable_vector_base object. |
| observable_vector_base::GetMany function | Retrieves a collection of elements in the observable_vector_base object beginning at the given index. |
| observable_vector_base::GetView function | Retrieves an immutable view of the observable_vector_base object. |
| observable_vector_base::IndexOf function | Retrieves the index of a specified element in the observable_vector_base object. |
| observable_vector_base::InsertAt function | Inserts an element at the specified index in the observable_vector_base object. |
| observable_vector_base::RemoveAt function | Removes the element at the specified index in the observable_vector_base object. |
| observable_vector_base::RemoveAtEnd function | Removes the last element from the observable_vector_base object. |
| observable_vector_base::ReplaceAll function | Replaces all the elements in the observable_vector_base object with the specified elements. |
| observable_vector_base::SetAt function | Sets the value of the element at the specified index in the observable_vector_base object. |
| observable_vector_base::Size function | Retrieves the number of elements in the observable_vector_base object. |
| observable_vector_base::VectorChanged function | Registers and revokes a delegate that handles the vector-changed event of the observable_vector_base object. |
Iterators
A observable_vector_base is a range, and that range is defined by internal free functions (each of which retrieves an iterator) that are compatible with standard language features. Because of this, you can enumerate the elements in a observable_vector_base object with a range-based for statement.
You can also retrieve an IIterator from the observable_vector_base::First function, and use that to iterate through the elements in a observable_vector_base object.
...
#include <iostream>
using namespace winrt;
using namespace Windows::Foundation::Collections;
...
struct MyObservableVector :
implements<MyObservableVector, IObservableVector<float>, IVector<float>, IVectorView<float>, IIterable<float>>,
winrt::observable_vector_base<MyObservableVector, float>
{
auto& get_container() const noexcept
{
return m_values;
}
auto& get_container() noexcept
{
return m_values;
}
private:
std::vector<float> m_values{ 0.1f, 0.2f, 0.3f };
};
...
IObservableVector<float> coll{ winrt::make<MyObservableVector>() };
for (auto const& el : coll)
{
std::wcout << el << std::endl;
}
IIterator<float> it{ coll.First() };
while (it.HasCurrent())
{
std::wcout << it.Current() << std::endl;
it.MoveNext();
}
observable_vector_base::Append function
Appends an element to the end of the observable_vector_base object.
Syntax
void Append(T const& value);
Parameters
value
The element to append.
observable_vector_base::Clear function
Removes all elements from the observable_vector_base object.
Syntax
void Clear() noexcept;
observable_vector_base::First function
Retrieves an IIterator representing the first element in the observable_vector_base object.
Syntax
auto First();
Return value
An IIterator representing the first element in the observable_vector_base object.
observable_vector_base::GetAt function
Retrieves the element at the specified index in the observable_vector_base object.
Syntax
T GetAt(uint32_t const index) const;
Parameters
index
A zero-based element index.
Return value
The element at the specified index in the observable_vector_base object.
observable_vector_base::GetMany function
Retrieves a collection of elements in the observable_vector_base object beginning at the given index.
Syntax
uint32_t GetMany(uint32_t const startIndex, array_view<T> values) const;
Parameters
startIndex
A zero-based element index to start at.
values
An array_view to copy the items into.
Return value
A value representing the number of elements retrieved.
observable_vector_base::GetView function
Retrieves an immutable view of the observable_vector_base object.
Syntax
winrt::Windows::Foundation::Collections::IVectorView<T> GetView() const noexcept;
Return value
An IVectorView containing an immutable view of the observable_vector_base.
observable_vector_base::IndexOf function
Retrieves the index of a specified element in the observable_vector_base object.
Syntax
bool IndexOf(T const& value, uint32_t& index) const noexcept;
Parameters
value
The element, in the observable_vector_base object, to look for.
index
The zero-based index of the element if the element is found, otherwise the number of elements in the observable_vector_base object.
Return value
true if the element is found, otherwise false.
observable_vector_base::InsertAt function
Inserts an element at the specified index in the observable_vector_base object.
Syntax
void InsertAt(uint32_t const index, T const& value);
Parameters
index
The zero-based index at which to insert the element.
value
The element to insert.
observable_vector_base::RemoveAt function
Removes the element at the specified index in the observable_vector_base object.
Syntax
void RemoveAt(uint32_t const index);
Parameters
index
The zero-based index of the element to remove.
observable_vector_base::RemoveAtEnd function
Removes the last element from the observable_vector_base object.
Syntax
void RemoveAtEnd();
observable_vector_base::ReplaceAll function
Replaces all the elements in the observable_vector_base object with the specified elements.
Syntax
void ReplaceAll(array_view<T const> value);
Parameters
value
An array_view containing the new elements.
observable_vector_base::SetAt function
Sets the value of the element at the specified index in the observable_vector_base object.
Syntax
void SetAt(uint32_t const index, T const& value);
Parameters
index
The zero-based index of the element whose value to set.
value
The element value to set.
observable_vector_base::Size function
Retrieves the number of elements in the observable_vector_base object.
Syntax
uint32_t Size() const noexcept;
Return value
A value representing the number of elements in the observable_vector_base object.
observable_vector_base::VectorChanged function
Registers and/or revokes a delegate that handles the vector-changed event of the observable_vector_base object.
Syntax
// Register
winrt::event_token VectorChanged(winrt::Windows::Foundation::Collections::VectorChangedEventHandler<T> const& handler);
// Revoke with event_token
void VectorChanged(winrt::event_token const cookie);
// Revoke with event_revoker
VectorChanged_revoker VectorChanged(winrt::auto_revoke_t, winrt::Windows::Foundation::Collections::VectorChangedEventHandler<T> const& handler) const;
Return value
Either void, a winrt::event_token with which you can revoke a registered delegate, or a VectorChanged_revoker (a type alias for a winrt::event_revoker<IObservableVector<T>>) with which you can revoke a registered delegate.
Example
winrt::event_revoker<IObservableVector<float>> m_event_revoker;
...
m_event_revoker = coll.VectorChanged(winrt::auto_revoke, [this](IObservableVector<float> const&, IVectorChangedEventArgs const&)
{
...
});