Just a note, the NSAssert() Foundation function should only be called
from inside an Objective-C method... if your code is somewhere in an
Object-C class, this is fine, but if you're calling from inside a C-
callback function or another C helper function (since you're creating
a Library, this may be the case), and you want to use the Foundation
method instead of the libc method (that I described earlier), make
sure you use NSCAssert(myNum != nil, @"blah blah blah");
Also, to disable assertions in these cases, compile with -
DNS_BLOCK_ASSERTIONS
/jason
On Jun 12, 2008, at 02:51 , Graham Cox wrote:
NSNumber* myNum = nil;
/* stuff */
NSAssert( myNum != nil, @"some error message");
[myClass calc:myNum];
Messages to nil are safe - it will treat your number as having a
value of 0. Thus as long as you initialise it to nil, your code will
run without crashing though of course may give incorrect results. If
you don't initialise it to anything, it will almost certainly crash.
The compiler should be warning you about this - if not, make it do so.
G.
On 12 Jun 2008, at 3:50 pm, Ashley Perrien wrote:
Noob question: I'm putting together a small code library and I'm
trying to include some error checking in the methods; what I want
to protect against is the following:
NSNumber *myNum;
// Lots of code where I've forgotten to actually do anything with
myNum
results = [myClass someCalculationUsing: myNum];
myNum in this case is an object and does exist but it's not a
valid, usable argument. So in the implementation I'd like to have
something along the lines of:
if (myNum == nil)
NSLog(@"some error message");
but can't figure out what to check for that would get me into the
error message condition. Any suggestions?
Ashley Perrien
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