Nuria::Callback Class Reference

A modern style callback mechanism which can be bound to various method types including slots. More...

#include <callback.hpp>

Public Types
enum	Placeholder {   _1 = 0, _2, _3, _4,   _5, _6, _7, _8,   _9, _10 }
enum	Type {   Invalid = 0, StaticMethod = 1, MemberMethod = 2, Slot = 3,   Lambda = 4 }

Public Member Functions
	Callback ()
	Callback (QObject *receiver, const char *slot, bool variadic=false, Qt::ConnectionType connectionType=Qt::AutoConnection)
	Callback (const Callback &other)
template<typename Ret , typename... Args>
	Callback (Ret(*func)(Args...), bool variadic=false)
template<typename Class , typename Ret , typename... Args>
	Callback (Class *instance, Ret(Class::*func)(Args...), bool variadic=false)
template<typename Class , typename Ret , typename... Args>
	Callback (Class *instance, Ret(Class::*func)(Args...) const, bool variadic=false)
template<typename Ret , typename... Args>
	Callback (const std::function< Ret(Args...) > &func, bool variadic=false)
	~Callback ()
QList< int >	argumentTypes () const
template<typename... Args>
Callback &	bind (const Args &...args)
void	bindList (const QVariantList &arguments=QVariantList())
QVariant	invoke (const QVariantList &arguments) const
bool	isValid () const
bool	isVariadic () const
template<typename... Args>
QVariant	operator() (const Args &...args) const
QVariant	operator() ()
Callback &	operator= (const Callback &other)
template<typename Ret , typename... Args>
Callback &	operator= (Ret(*func)(Args...))
bool	operator== (const Callback &other) const
int	returnType () const
template<typename Ret , typename... Args>
bool	setCallback (Ret(*func)(Args...))
template<typename Class , typename Ret , typename... Args>
bool	setCallback (Class *instance, Ret(Class::*func)(Args...) const)
template<typename Class , typename Ret , typename... Args>
bool	setCallback (Class *instance, Ret(Class::*func)(Args...))
template<typename Ret , typename... Args>
bool	setCallback (std::function< Ret(Args...) > func)
bool	setCallback (QObject *receiver, const char *slot, Qt::ConnectionType connectionType=Qt::AutoConnection)
void	setVariadic (bool variadic)
Type	type () const

Static Public Member Functions
template<typename Lambda , typename... Args>
static Callback	boundLambda (Lambda func, const Args &...args)
template<typename Lambda >
static Callback	fromLambda (Lambda l, bool variadic=false)

Friends
class	CallbackPrivate

Detailed Description

A modern style callback mechanism which can be bound to various method types including slots.

The Nuria::Callback class can be used when developers don't want to use the default signal/slots mechanism Qt provides for various reasons. Callback is designed to mimic parts of the std::function methods which makes it easy to use.

Note

This class is explicitly shared. This means that changes to the instance will not copy the data, but instead alter the instance directly.

Methods

Callback can be created out of all available method types - Essentially everything that has a operator(). This includes:

• Static methods, including static member methods
• Class member methods
• QObject slots
• std::function
• Lambdas

For all of the above types Callback provides a convenient constructors with the exception of lambdas (See fromLambda).

Argument and return types

Please note that all types which are passed to or from the callback must be registered to the Qt Meta System using the Q_DECLARE_METATYPE macro.

Another point is that Callback will always try its best to invoke a method. Passed arguments are checked if they match the type of the target method. If a argument doesn't, Callback will try to use QVariant::convert to convert the passed argument to the expected argument type. If this still fails, it will construct a temporary instance of the expected type and passes it instead, silently discarding the original argument.

It is also possible to use variadic callbacks. This means that on invocation, all passed arguments are packed into a single QVariantList. This list is now treated as it would've been passed as only argument, meaning that bound variables are applied after this process. The placeholder _1 points to the QVariantList.

Binding

Just like std::function Callback supports a mechanism to bind arguments to a callback. Placeholders are also supported (Using _1, ..., _10).

See also

bind boundLambda

Behaviour with QObject slots

When a callback uses a slot as target method, it can be used for thread to thread communication. If the slot returns void (nothing), then the slot will be invoked using a Qt::QueuedConnection, that means, the caller won't be blocked until the callee (The slot) has finished its operation. If the callee returns something different than a void, then the caller will be blocked until the callee finished and returned the result to the calling thread.

Multi-threading

Callback is re-entrant. Do not change a instance from multiple threads concurrently. Target methods will be invoked in the calling thread, when not using a QObject slot as target.

Member Enumeration Documentation

enum Nuria::Callback::Placeholder

Placeholders for bind().

enum Nuria::Callback::Type

Possible types of callbacks.

Enumerator
StaticMethod	Invalid instance.
MemberMethod	Invokes a static method.
Slot	Invokes a member method.
Lambda	Invokes a slot.

Constructor & Destructor Documentation

Nuria::Callback::Callback

(

)

Constructs an invalid instance.

Nuria::Callback::Callback	(	QObject *	receiver,
		const char *	slot,
		bool	variadic = false,
		Qt::ConnectionType	connectionType = Qt::AutoConnection
	)

Constructs a callback out of a slot.

Warning

If you want to set the connectionType manually make sure you pass a value for variadic. Else, the compiler may choose to implicitly cast the Qt::ConnectionType to bool!

Nuria::Callback::Callback

(

const Callback &

other

)

Copy constructor.

template<typename Ret , typename... Args>

Nuria::Callback::Callback ( Ret(*)(Args...)  func, bool  variadic = false  )

inline

Constructs a callback from a static method.

template<typename Class , typename Ret , typename... Args>

Nuria::Callback::Callback ( Class *  instance, Ret(Class::*)(Args...)  func, bool  variadic = false  )

inline

Constructs a callback from a member method.

template<typename Class , typename Ret , typename... Args>

Nuria::Callback::Callback ( Class *  instance, Ret(Class::*)(Args...) const  func, bool  variadic = false  )

inline

Constructs a callback from a constant member method.

Nuria::Callback::~Callback

(

)

Destructor.

Member Function Documentation

QList< int > Nuria::Callback::argumentTypes

(

)

const

Returns a list of arguments expected by this callback.

template<typename... Args>

Callback& Nuria::Callback::bind ( const Args &...  args )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. This method offers a more std::bind-like functionality. Use bindList if you have a QVariantList of these arguments.

void Nuria::Callback::bindList

(

const QVariantList &

arguments = QVariantList()

)

Binds arguments to the callback. This essentially works like std::bind(). If no placeholders are used additional arguments are appended to the final argument list when invoked. If placeholders are used only the arguments whose positions are set with a placeholder are passed, the others are silently discarded.

template<typename Lambda , typename... Args>

static Callback Nuria::Callback::boundLambda ( Lambda  func, const Args &...  args  )

inlinestatic

Takes a lambda and returns a Callback with args already bound.

template<typename Lambda >

static Callback Nuria::Callback::fromLambda ( Lambda  l, bool  variadic = false  )

inlinestatic

Constructs a callback out of a lambda.

QVariant Nuria::Callback::invoke

(

const QVariantList &

arguments

)

const

Invokes the callback using arguments. Use this method if you have the arguments themself as list.

See also

operator()

bool Nuria::Callback::isValid

(

)

const

Returns true when this callback is valid i.e. callable.

bool Nuria::Callback::isVariadic

(

)

const

Returns if this callback is variadic.

template<typename... Args>

QVariant Nuria::Callback::operator() ( const Args &...  args ) const

inline

Invokes the callback method, passing args.

QVariant Nuria::Callback::operator() ( )

inline

Invokes the callback without arguments.

Callback& Nuria::Callback::operator=

(

const Callback &

other

)

Assignment operator.

bool Nuria::Callback::operator==

(

const Callback &

other

)

const

Comparison operator.

Returns true if both callbacks point to the very same method (and instance).

Warning

Bound arguments aren't taken into account for this operation.

int Nuria::Callback::returnType

(

)

const

Returns the return-type of the callback.

void Nuria::Callback::setVariadic

(

bool

variadic

)

Sets if this callback is variadic or not.

Type Nuria::Callback::type

(

)

const

Returns the type of this callback.

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

• callback.hpp