Template Struct FieldBase< Array< U > >

Struct Documentation

template<typename U>
struct FieldBase<Array<U>>

Field base class specialization for arrays.

The Array tag is used for both fixed-length (same size in every record, accessible via ColumnView) and variable-length arrays; variable-length arrays are initialized with a size of 0. Ideally, we’d use complete different tag classes for those two very different types, but boost::variant and boost::mpl put a limit of 20 on the number of field types, and we’re running out. In a future reimplementation of afw::table, we should fix this.

Public Types

typedef ndarray::Array<U const, 1, 1> Value

the type returned by BaseRecord::get

typedef ndarray::ArrayRef<U, 1, 1> Reference

the type returned by BaseRecord::operator[]

typedef ndarray::ArrayRef<U const, 1, 1> ConstReference

the type returned by BaseRecord::operator[] (const)

typedef U Element

the type of subfields and array elements

Public Functions

FieldBase(int size = 0)

Construct a FieldBase with the given size.

A size == 0 indicates a variable-length array. Negative sizes are not permitted.

This constructor is implicit with a default so it can be used in the Field constructor (as if it were an int argument) without specializing Field. In other words, it allows one to construct a 25-element array field like this: 

Field< Array<float> >("name", "documentation", 25);

…even though the third argument to the Field constructor takes a FieldBase, not an int.

FieldBase(FieldBase const&)
FieldBase(FieldBase&&)
FieldBase &operator=(FieldBase const&)
FieldBase &operator=(FieldBase&&)
~FieldBase()
int getElementCount() const

Return the number of subfield elements (equal to the size of the array), or 0 for a variable-length array.

int getSize() const

Return the size of the array (equal to the number of subfield elements), or 0 for a variable-length array.

bool isVariableLength() const

Return true if the field is variable-length (each record can have a different size array).

Public Static Functions

static std::string getTypeString()

Return a string description of the field type.

Protected Functions

void stream(std::ostream &os) const

Defines how Fields are printed.

Reference getReference(Element *p, ndarray::Manager::Ptr const &m) const

Used to implement BaseRecord::operator[] (non-const).

ConstReference getConstReference(Element const *p, ndarray::Manager::Ptr const &m) const

Used to implement BaseRecord::operator[] (const).

Value getValue(Element const *p, ndarray::Manager::Ptr const &m) const

Used to implement BaseRecord::get.

void setValue(Element *p, ndarray::Manager::Ptr const&, ndarray::Array<Element, 1, 1> const &value) const

Used to implement BaseRecord::set; accepts only non-const arrays of the right type. Fixed-length arrays are handled by copying the data from value to p through p + _size. Variable-length arrays are handled by setting p to the address of value, an ndarray, hence a shallow copy (ndarray arrays are reference-counted so this will not leak memory). If you want deep assignment of variable-length data, use operator[] to get a reference and assign to that.

template<typename Derived>
void setValue(Element *p, ndarray::Manager::Ptr const&, ndarray::ExpressionBase<Derived> const &value) const

Used to implement BaseRecord::set; accepts any ndarray expression.

Protected Static Functions

static FieldBase makeDefault()

Needed to allow Keys to be default-constructed.