Question
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Closed 11 years ago.
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[Underscore prefix on property name?](https://stackoverflow.com/questions/5582448/underscore-prefix-on- property-name)
What does this mean? @synthesize window=_window; I know that in general it
means that 'some class' has a window, but why use _window instead of just
window? Is this a namespace thing?
Answer
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].
