Is CALayer insertSublayer: atindex: destructive?

问题:

The documentation is not clear on what happens the the layer currently atindex:xy when using insertSublayer:abc.layer atindex:xy. My experimentation has had mixed results. My understanding is index 0 is furthest from the user (all other layers would be above that one).

If I call insertSublayer:abc.layer atindex:0, and def.layer is already at index:0, does def.layer get destroyed, or shifted to index:1?

Thanks.

回答1:

It is not destructive. insertSublayer:atIndex: just inserts that sublayer at that index in the sublayers array, and has all the normal behavior associated with array insertion in an NSMutableArray

回答2:

def.layer gets shifted to index:1, insertSublayer does simple insertion, NOT replacement.