From a72d585f9b3327d301a605e9500058670ed7a5f5 Mon Sep 17 00:00:00 2001 From: Sze Howe Koh Date: Mon, 1 Sep 2014 17:52:01 +0800 Subject: Doc: Restructure "Signal & Slots" article Put sections with similar content together: - Put "A Small Example" next to "A Real Example". - Put "Signals and Slots", "Signals", and "Slots" together. Altogether, these 3 sections contain lots of repeated content and should be consolidated in a future commit. This patch only moves content around without adding, removing, or modifying content. Change-Id: Ic6bf6a8b51f4785a8bbe6d230c2934f2c952104d Reviewed-by: Jerome Pasion --- .../doc/src/objectmodel/signalsandslots.qdoc | 141 +++++++++++---------- 1 file changed, 71 insertions(+), 70 deletions(-) (limited to 'src/corelib/doc') diff --git a/src/corelib/doc/src/objectmodel/signalsandslots.qdoc b/src/corelib/doc/src/objectmodel/signalsandslots.qdoc index 6f0e230943..6dcf567c2e 100644 --- a/src/corelib/doc/src/objectmodel/signalsandslots.qdoc +++ b/src/corelib/doc/src/objectmodel/signalsandslots.qdoc @@ -113,76 +113,6 @@ Together, signals and slots make up a powerful component programming mechanism. - \section1 A Small Example - - A minimal C++ class declaration might read: - - \snippet signalsandslots/signalsandslots.h 0 - - A small QObject-based class might read: - - \snippet signalsandslots/signalsandslots.h 1 - \codeline - \snippet signalsandslots/signalsandslots.h 2 - \snippet signalsandslots/signalsandslots.h 3 - - The QObject-based version has the same internal state, and provides - public methods to access the state, but in addition it has support - for component programming using signals and slots. This class can - tell the outside world that its state has changed by emitting a - signal, \c{valueChanged()}, and it has a slot which other objects - can send signals to. - - All classes that contain signals or slots must mention - Q_OBJECT at the top of their declaration. They must also derive - (directly or indirectly) from QObject. - - Slots are implemented by the application programmer. - Here is a possible implementation of the \c{Counter::setValue()} - slot: - - \snippet signalsandslots/signalsandslots.cpp 0 - - The \c{emit} line emits the signal \c valueChanged() from the - object, with the new value as argument. - - In the following code snippet, we create two \c Counter objects - and connect the first object's \c valueChanged() signal to the - second object's \c setValue() slot using QObject::connect(): - - \snippet signalsandslots/signalsandslots.cpp 1 - \snippet signalsandslots/signalsandslots.cpp 2 - \codeline - \snippet signalsandslots/signalsandslots.cpp 3 - \snippet signalsandslots/signalsandslots.cpp 4 - - Calling \c{a.setValue(12)} makes \c{a} emit a - \c{valueChanged(12)} signal, which \c{b} will receive in its - \c{setValue()} slot, i.e. \c{b.setValue(12)} is called. Then - \c{b} emits the same \c{valueChanged()} signal, but since no slot - has been connected to \c{b}'s \c{valueChanged()} signal, the - signal is ignored. - - Note that the \c{setValue()} function sets the value and emits - the signal only if \c{value != m_value}. This prevents infinite - looping in the case of cyclic connections (e.g., if - \c{b.valueChanged()} were connected to \c{a.setValue()}). - - By default, for every connection you make, a signal is emitted; - two signals are emitted for duplicate connections. You can break - all of these connections with a single disconnect() call. - If you pass the Qt::UniqueConnection \a type, the connection will only - be made if it is not a duplicate. If there is already a duplicate - (exact same signal to the exact same slot on the same objects), - the connection will fail and connect will return false - - This example illustrates that objects can work together without needing to - know any information about each other. To enable this, the objects only - need to be connected together, and this can be achieved with some simple - QObject::connect() function calls, or with \c{uic}'s - \l{Using a Designer UI File in Your Application#Automatic Connections} - {automatic connections} feature. - \section1 Signals @@ -258,6 +188,77 @@ #undef the offending preprocessor symbol. + \section1 A Small Example + + A minimal C++ class declaration might read: + + \snippet signalsandslots/signalsandslots.h 0 + + A small QObject-based class might read: + + \snippet signalsandslots/signalsandslots.h 1 + \codeline + \snippet signalsandslots/signalsandslots.h 2 + \snippet signalsandslots/signalsandslots.h 3 + + The QObject-based version has the same internal state, and provides + public methods to access the state, but in addition it has support + for component programming using signals and slots. This class can + tell the outside world that its state has changed by emitting a + signal, \c{valueChanged()}, and it has a slot which other objects + can send signals to. + + All classes that contain signals or slots must mention + Q_OBJECT at the top of their declaration. They must also derive + (directly or indirectly) from QObject. + + Slots are implemented by the application programmer. + Here is a possible implementation of the \c{Counter::setValue()} + slot: + + \snippet signalsandslots/signalsandslots.cpp 0 + + The \c{emit} line emits the signal \c valueChanged() from the + object, with the new value as argument. + + In the following code snippet, we create two \c Counter objects + and connect the first object's \c valueChanged() signal to the + second object's \c setValue() slot using QObject::connect(): + + \snippet signalsandslots/signalsandslots.cpp 1 + \snippet signalsandslots/signalsandslots.cpp 2 + \codeline + \snippet signalsandslots/signalsandslots.cpp 3 + \snippet signalsandslots/signalsandslots.cpp 4 + + Calling \c{a.setValue(12)} makes \c{a} emit a + \c{valueChanged(12)} signal, which \c{b} will receive in its + \c{setValue()} slot, i.e. \c{b.setValue(12)} is called. Then + \c{b} emits the same \c{valueChanged()} signal, but since no slot + has been connected to \c{b}'s \c{valueChanged()} signal, the + signal is ignored. + + Note that the \c{setValue()} function sets the value and emits + the signal only if \c{value != m_value}. This prevents infinite + looping in the case of cyclic connections (e.g., if + \c{b.valueChanged()} were connected to \c{a.setValue()}). + + By default, for every connection you make, a signal is emitted; + two signals are emitted for duplicate connections. You can break + all of these connections with a single disconnect() call. + If you pass the Qt::UniqueConnection \a type, the connection will only + be made if it is not a duplicate. If there is already a duplicate + (exact same signal to the exact same slot on the same objects), + the connection will fail and connect will return false + + This example illustrates that objects can work together without needing to + know any information about each other. To enable this, the objects only + need to be connected together, and this can be achieved with some simple + QObject::connect() function calls, or with \c{uic}'s + \l{Using a Designer UI File in Your Application#Automatic Connections} + {automatic connections} feature. + + \section1 A Real Example Here is a simple commented example of a widget. -- cgit v1.2.3