Containers¶
Description¶
The Container type is used when a column source needs to store a list rather than a scalar element. Such a situation arises, for example, when you have a Deephaven group_by operation.
In this situation you will have a
ContainerBaseColumnSource
representing the column. To get the data out, you will use
FillChunk
to fill a
ContainerBaseChunk.
Now you will have a Chunk containing the lists you want to look at.
Each of the elements in this Chunk is a
std::shared_ptr<ContainerBase>
However, to get at the elements inside these lists, you need to downcast the
std::shared_ptr<ContainerBase>
to the correct derived type, e.g.
std::shared_ptr< Container <int32_t>>.
If you already know the element type you need, you can use a method like
AsContainerPtr
to downcast it directly. If not, you can use the
ContainerVisitor
to determine the type at runtime. Another way of determining the type at runtime is to use the
ColumnSource’s
GetElementType
method. The
ElementType
you get will represent a list type, and you can use its
Id method to retrieve its
ElementTypeId::Enum.
Declarations¶
-
class ContainerBase : public std::enable_shared_from_this<ContainerBase>¶
Abstract class for the Deephaven Container type.
Subclassed by deephaven::dhcore::container::Container< T >
Public Functions
-
inline size_t size() const¶
Returns the number of elements in the container.
- Returns:
The number of elements in the Container
If this object is a Container<T>, returns a shared_ptr<const Container<T>> pointing to this object. Otherwise, returns a null shared_ptr.
- Returns:
A shared_ptr<const Container<T>> if this object is a Container<T>, otherwise a null shared_ptr.
-
template<class T>
inline const Container<T> &AsContainer() const¶ If this object is a Container<T>, returns a const Container<T>& referring to this object. Otherwise, throws an exception.
- Returns:
A const Container<T>& referring to this object.
-
virtual void AcceptVisitor(ContainerVisitor *visitor) const = 0¶
Implements the Visitor pattern.
-
inline size_t size() const¶
-
template<typename T>
class Container : public deephaven::dhcore::container::ContainerBase¶ Forward declaration
- Template Parameters:
T –
Public Functions
Constructor. This constructor is effectively private because outside callers cannot create the dummy “Private” argument.
-
inline virtual void AcceptVisitor(ContainerVisitor *visitor) const final¶
Implement the Visitor pattern.
-
inline const T &operator[](size_t index) const¶
Indexing operator
- Parameters:
index – Index of the specified element
- Returns:
a const reference to the specified element
-
inline bool IsNull(size_t index) const¶
Determines if the element at the specified index is null.
- Parameters:
index – Index of the specified element
- Returns:
true if the element at the specified index is null; false otherwise
-
inline const T *data() const¶
Gets a const pointer to the start of the data
- Returns:
A const pointer to the start of the data
Public Static Functions
Creates a Container<T> of the specified size from the corresponding data and nulls arrays.
- Parameters:
data – A shared_ptr to the underlying data
nulls – A shared_ptr to the nulls flags
size – The size of the container
- Returns:
A shared_ptr<Container<T>> representing the specified data.