The property class provides several meta information about a property and gives read/write access to its value. More...

#include <property.h>

Public Member Functions
access_levels	get_access_level () const noexcept
	Returns the access level with which this property was registered. More...

type	get_declaring_type () const noexcept
	Returns the type of the class or struct that declares this property. More...

enumeration	get_enumeration () const noexcept
	Returns the enumerator if this property is an enum type; otherwise the returned value is not valid. More...

variant	get_metadata (const variant &key) const
	Returns the meta data for the given key `key`. More...

string_view	get_name () const noexcept
	Returns the name of this property. More...

type	get_type () const noexcept
	Returns the underlying type object of this property. More...

variant	get_value (instance object) const
	Returns the current property value of the given instance `object`. More...

bool	is_enumeration () const noexcept
	Returns true if the underlying property is an enumeration. More...

bool	is_readonly () const noexcept
	Returns true if this property is read only, otherwise false. More...

bool	is_static () const noexcept
	Returns true if this property is static property, otherwise false. More...

bool	is_valid () const noexcept
	Returns true if this property is valid, otherwise false. More...

	operator bool () const noexcept
	Convenience function to check if this property is valid or not. More...

bool	operator!= (const property &other) const noexcept
	Returns true if this property is the not the same like the `other`. More...

bool	operator== (const property &other) const noexcept
	Returns true if this property is the same like the `other`. More...

bool	set_value (instance object, argument arg) const
	Set the property of the given instance `object` to the given value `arg`. More...

Detailed Description

The property class provides several meta information about a property and gives read/write access to its value.

A instance of a property class can only be obtained from the type class. See type::get_property() and type::get_properties().

For registration a property, nested inside a class, see registration::class_<T>::property() and for global properties see registration::property().

Meta Information

A property has a name, and a type as well as attributes that specify its behavior: is_readonly(), is_static(), is_enumeration(), is_array(). When the property was declared inside a class, then get_declaring_type() can be used to obtain the type of this class.

The property's values are set and retrieved with set_value() and get_value(); When its not a static property you have to provide a class instance to set/get the property value. This instance can be the raw type on the stack; the current hierarchy level doesn't matter. It can be also a raw pointer to the object or a variant which contains the instance, again as pointer or stack object. When the property is declared as static you you still have to provide an empty instance object, use therefore the default ctor of instance(), or as shortcut use simply {}.

A property will be successfully set when the provided instance can be converted to the declared class type. The new forwarded property value must 100% match the type of the registered property. An automatically type conversion is not performed.

The return type of get_value() is variant object. This object contains not only the value of the property, it also indicates whether the property value could be retrieved or not. A valid variant object means, that the property was successfully retrieved, otherwise not.

Another way to get access a property is through type's set and get functions. See type::set_property_value() and type::get_property_value() for details.

Copying and Assignment

A property object is lightweight and can be copied by value. However, each copy will refer to the same underlying property.

Typical Usage

using namespace rttr;
struct MyStruct { int value = 23; };
//...
variant obj = type::get_by_name("MyStruct").create({});
property prop = type::get_by_name("MyStruct").get_property("value");
if (prop)
{
   variant val = prop.get_value(obj);
   std::cout << val.get_value<int>(); // prints 23
   MyStruct inst;
   val = prop.set_value(inst, 42);
   std::cout << inst.value; // prints 42
   // or as pointer
   MyStruct* ptr = &inst;
   val = prop.set_value(ptr, 7);
   std::cout << ptr->value; // prints 7
   // or do it all in one call
   type::get(inst).set_propert_value("value", inst, 1024);
   std::cout << inst.value; // prints 1024
}

See also: method, enumeration, constructor and type

Member Function Documentation

access_levels rttr::property::get_access_level ( ) const

noexcept

Returns the access level with which this property was registered.

Remarks: When the property is not valid, this function will return level access_levels::public_access.

Returns: access_levels of the property.

type rttr::property::get_declaring_type ( ) const

noexcept

Returns the type of the class or struct that declares this property.

Remarks: When this property does not belong to a class (i.e. is a global property) it will return an invalid type object. When this property is not valid, this function will return an invalid type object (see type::is_valid).

Returns: Type of the declaring class/struct for this property.

enumeration rttr::property::get_enumeration ( ) const

noexcept

Returns the enumerator if this property is an enum type; otherwise the returned value is not valid.

See also: is_enumeration()

Returns: An enumeration object.

variant rttr::property::get_metadata ( const variant & key ) const

Returns the meta data for the given key key.

Remarks: When no meta data is registered with the given key, an invalid variant object is returned (see variant::is_valid).

Returns: A variant object, containing arbitrary data.

string_view rttr::property::get_name ( ) const

noexcept

Returns the name of this property.

Remarks: When the property is not valid, this function will return an empty string_view.

Returns: Name of the property.

type rttr::property::get_type ( ) const

noexcept

Returns the underlying type object of this property.

Remarks: When the property is not valid, this function will return an invalid type object.

Returns: Type of the underlying property.

variant rttr::property::get_value ( instance object ) const

Returns the current property value of the given instance object.

Remarks: When the property is static, you can forward an empty instance.

See also: set_value().

Returns: The property value of the given instance object.

bool rttr::property::is_enumeration ( ) const

noexcept

Returns true if the underlying property is an enumeration.

Remarks: When the property is not valid, this function will return false.

Returns: True if this is a enumeration type, otherwise false.

bool rttr::property::is_readonly ( ) const

noexcept

Returns true if this property is read only, otherwise false.

Remarks: When the property is not valid, this function will return false.

Returns: True if this is a read only property, otherwise false.

bool rttr::property::is_static ( ) const

noexcept

Returns true if this property is static property, otherwise false.

A static property does not need an instance for performing set_value/get_value.

Remarks: When the property is not valid, this function will return false.

Returns: True if this is a static property, otherwise false.

bool rttr::property::is_valid ( ) const

noexcept

Returns true if this property is valid, otherwise false.

Returns: True if this property is valid, otherwise false.

rttr::property::operator bool ( ) const

explicitnoexcept

Convenience function to check if this property is valid or not.

Returns: True if this property is valid, otherwise false.

bool rttr::property::operator!= ( const property & other ) const

noexcept

Returns true if this property is the not the same like the other.

Returns: True if both properties are different, otherwise false.

bool rttr::property::operator== ( const property & other ) const

noexcept

Returns true if this property is the same like the other.

Returns: True if both properties are equal, otherwise false.

bool rttr::property::set_value	(	instance	object,
		argument	arg
	)		const

Set the property of the given instance object to the given value arg.

Remarks: When the property is declared as read only this function will return false. When you have a static property just pass an empty instance as object argument. When the property is not valid, this function will return false.

See also: get_value().

Returns: The return value indicates whether the operation was successful or not.

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

property.h

Public Member Functions

Detailed Description

Meta Information

Copying and Assignment

Typical Usage

Member Function Documentation