Question

I am new to Objective C. On one of the developers documentation, I found the following statemenet.

The following statement invokes the lockFocusIfCanDraw method and assigns the return value to
flag. It does not generate a compiler warning unless there is a mismatch between the type for flag
and the method’s return type. Nonetheless, this pattern is strongly discouraged.

flag = aView.lockFocusIfCanDraw;

In addition to the one above, I can think of many situations of this kind. For instance I might want to capture the display text from a box and assign it to a local string etc.

I am just wondering, if the above statement is discouraged, what is the recommended way of handling such situation?

Answer 1

The dot syntax for calling methods should only be used for properties (i.e. when calling accessors). Since lockFocusIfCanDraw is not an accessor method, you should use the regular square brackets syntax, i.e. flag = [aView lockFocusIfCanDraw]; instead.