mangrove::comparison_expr< NvpT, U > Class Template Reference

Represents a query expression with the syntax "key: {$op: value}". More...

#include <query_builder.hpp>

Inheritance diagram for mangrove::comparison_expr< NvpT, U >:

Public Member Functions
constexpr	comparison_expr (const NvpT &nvp, const U &field, const char *op)
	Constructs a query expression for the given key, value, and comparison type. More...
constexpr	comparison_expr (const comparison_expr &expr, const char *op)
	Takes a comparison expression, and creates a new one with a different operator, but the same value and field. More...
std::string &	append_name (std::string &s) const
	Appends the name of the contained field to a string.
void	append_to_bson (bsoncxx::builder::core &builder, bool wrap=false, bool omit_name=false) const
	Appends this expression to a BSON core builder, as a key-value pair of the form "key: {$cmp: val}", where $cmp is some comparison operator. More...
	operator bsoncxx::document::view_or_value () const
	Converts the expression to a BSON filter for a query. More...

Detailed Description

template<typename NvpT, typename U>
class mangrove::comparison_expr< NvpT, U >

Represents a query expression with the syntax "key: {$op: value}".

This usually means queries that are comparisons, such as (User.age > 21). However, this also covers operators such as $exists, or any operator that has the above syntax.

Template Parameters

NvpT	The type of the name-value pair this expression uses.
U	The type of the value to compare against. This could be the same as the value type of NvpT, or the type of some other parameter, or even a query builder expression.

Constructor & Destructor Documentation

template<typename NvpT, typename U>

constexpr mangrove::comparison_expr< NvpT, U >::comparison_expr ( const NvpT &  nvp, const U &  field, const char *  op  )

inline

Constructs a query expression for the given key, value, and comparison type.

Parameters

nvp	A name-value pair corresponding to a key in a document
field	The value that the key is being compared to.
op	The type of comparison operator, such at gt (>) or ne (!=).

template<typename NvpT, typename U>

constexpr mangrove::comparison_expr< NvpT, U >::comparison_expr ( const comparison_expr< NvpT, U > &  expr, const char *  op  )

inline

Takes a comparison expression, and creates a new one with a different operator, but the same value and field.

This is primarily used to wrap $regex operators in $not, since $not cannot contains a $regex operator, it must directly contain the regex itself.

Parameters

expr	A comparison expresison with a similar field type and value type.
op	The new operator to use.

Member Function Documentation

template<typename NvpT, typename U>

void mangrove::comparison_expr< NvpT, U >::append_to_bson ( bsoncxx::builder::core &  builder, bool  wrap = false, bool  omit_name = false  ) const

inline

Appends this expression to a BSON core builder, as a key-value pair of the form "key: {$cmp: val}", where $cmp is some comparison operator.

Parameters

builder	A BSON core builder
wrap	Whether to wrap the BSON inside a document.
omit_name	Whether to skip the name of the field. This is used primarily in not_expr and free_expr to append just the value of the expression.

template<typename NvpT, typename U>

mangrove::comparison_expr< NvpT, U >::operator bsoncxx::document::view_or_value ( ) const

inline

Converts the expression to a BSON filter for a query.

The format of the BSON is "{key: {$not: {$cmp: val}}}".

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The documentation for this class was generated from the following files:

• src/mangrove/expression_syntax.hpp
• src/mangrove/query_builder.hpp