[#BloombergLP-bdld-DatumMapRef]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdld.adoc[bdld]::DatumMapRef
:relfileprefix: ../../
:mrdocs:

Read‐only view of a map of `Datum` values keyed by strings.

== Synopsis

Declared in `<bdld_datum.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class DatumMapRef;
----

== Description

This class provides a read‐only view to a map of datums (an array of `DatumMapEntry` objects). It holds the array by a `const` pointer and an integral size value. It acts as return value for accessors inside the `Datum` class that return a map of `Datum` objects. Note that zero‐size maps are valid.

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdld/DatumMapRef/SizeType.adoc[`SizeType`] 
| Unsigned integral type for capacities, key sizes, and string lengths.
| xref:BloombergLP/bdld/DatumMapRef/const_iterator.adoc[`const_iterator`] 
| Const iterator for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/const_pointer.adoc[`const_pointer`] 
| Const pointer to a map entry.
| xref:BloombergLP/bdld/DatumMapRef/const_reference.adoc[`const_reference`] 
| Const reference to a map entry.
| xref:BloombergLP/bdld/DatumMapRef/const_reverse_iterator.adoc[`const_reverse_iterator`] 
| Const reverse iterator for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/difference_type.adoc[`difference_type`] 
| Iterator difference type for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/element_type.adoc[`element_type`] 
| This `typedef` is an alias for `element_type`.
| xref:BloombergLP/bdld/DatumMapRef/iterator.adoc[`iterator`] 
| Iterator for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/pointer.adoc[`pointer`] 
| Pointer to a map entry.
| xref:BloombergLP/bdld/DatumMapRef/reference.adoc[`reference`] 
| Reference to a map entry.
| xref:BloombergLP/bdld/DatumMapRef/reverse_iterator.adoc[`reverse_iterator`] 
| Reverse iterator for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/size_type.adoc[`size_type`] 
| Size type for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/value_type.adoc[`value_type`] 
| Value type for this map reference.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdld/DatumMapRef/2constructor.adoc[`DatumMapRef`]         [.small]#[constructor]#
| Create a read‐only view of the specified datum map.
| xref:BloombergLP/bdld/DatumMapRef/back.adoc[`back`] 
| Return a reference providing non‐modifiable access to the last element of the map this reference object represents. The behavior is undefined unless `size() > 0`.
| xref:BloombergLP/bdld/DatumMapRef/begin.adoc[`begin`] 
| Return an iterator to the first map entry.
| xref:BloombergLP/bdld/DatumMapRef/cbegin.adoc[`cbegin`] 
| Return an iterator to the first entry of this map.
| xref:BloombergLP/bdld/DatumMapRef/cend.adoc[`cend`] 
| Return an iterator providing non‐modifiable access pointing past‐the‐end of the array this reference object represents.
| xref:BloombergLP/bdld/DatumMapRef/crbegin.adoc[`crbegin`] 
| Return a reverse iterator to the last entry of this map.
| xref:BloombergLP/bdld/DatumMapRef/crend.adoc[`crend`] 
| Return a reverse iterator providing non‐modifiable access pointing past‐the‐end of the array this reference object represents.
| xref:BloombergLP/bdld/DatumMapRef/data.adoc[`data`] 
| Return a pointer to the first entry of this map.
| xref:BloombergLP/bdld/DatumMapRef/empty.adoc[`empty`] 
| Return `size() == 0`.
| xref:BloombergLP/bdld/DatumMapRef/end.adoc[`end`] 
| Return a past‐the‐end iterator for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/find.adoc[`find`] 
| Return a pointer to the datum with the specified `key`, or null.
| xref:BloombergLP/bdld/DatumMapRef/front.adoc[`front`] 
| Return a reference to the first entry of this map.
| xref:BloombergLP/bdld/DatumMapRef/isSorted.adoc[`isSorted`] 
| Return `true` if underlying map is sorted and `false` otherwise.
| xref:BloombergLP/bdld/DatumMapRef/operator_subs.adoc[`operator[]`] 
| Return a reference to the map entry at the specified `position`.
| xref:BloombergLP/bdld/DatumMapRef/ownsKeys.adoc[`ownsKeys`] 
| Return `true` if underlying map owns the keys and `false` otherwise. Note that `false` is always returned for zero‐sized `DatumMapRef`.
| xref:BloombergLP/bdld/DatumMapRef/print.adoc[`print`] 
| Format this object to the specified output stream.
| xref:BloombergLP/bdld/DatumMapRef/rbegin.adoc[`rbegin`] 
| Return a reverse iterator to the last map entry.
| xref:BloombergLP/bdld/DatumMapRef/rend.adoc[`rend`] 
| Return a past‐the‐end reverse iterator for this map reference.
| xref:BloombergLP/bdld/DatumMapRef/size.adoc[`size`] 
| Return a const‐pointer to the number of elements of the map this reference object represents.
| xref:BloombergLP/bdld/DatumMapRef/2conversion.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<DatumMapRef, HasPrintMethod>`] 
| `DatumMapRef` is trivially copyable.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdld/operator_not_eq-0b.adoc[`operator!=`]
| Return whether `lhs` and `rhs` have different values.
| xref:BloombergLP/bdld/operator_eq-09.adoc[`operator==`]
| Return whether `lhs` and `rhs` have the same value.
|===


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