I’ll give a go at describing this programming convention in basic English.
It is a very common convention in other languages to name member variables with a preceding m
, m_
, or _
to distinguish them from locally declared variables and to signify that they should have accessors written, if necessary (no classInstance.m_Variable = 5
).
If an Objective-C programmer declares ivars following this convention (and they should) and uses the basic syntax @synthesize _window;
then the usage for the property becomes somewhat ugly: classInstance._window = myWindow
or [classInstance set_window:myWindow]
. Using the syntax @synthesize window=_window;
allows the Obj-C programmer to utilize a popular programming standard (preceding ivars with _
) while simultaneously having property accessors that use the Apple standard classInstance.window = myWindow
and [classInstance setWindow:myWindow]
.