[sidecar71]

I am new to Objective C (and C for that matter) and went through the apple tutorial for that language only to get the below error when trying to "build" the application.

----------
Building target "Currency Converter" with build style "Development" (optimization:level '0', debug-symbols:on) - (2 errors)

Missing file or directory: Currency
Missing file or directory: Currency_prefix.h
----------

What is it looking for? I dont see anything (an object or name or interface) that I have called "Currency".

These are the Classes that are in the left-hand column of project builder:
ConverterController.h
ConverterController.m
Converter.h
Converter.m
Currency Converter_prefix.h
main.m

It's probably my ignorance of C that is causing me to overlook something quite obvious.

[Also, can anyone recommend a good Objective C book? O'Reilly's?]

[techtrucker]

Might be the space in the Currency Converter class name...

[alien]

It's not your lacking knowledge of C

Unfortunately, there is a bug in the current Project Builder that gives this error with project names containing spaces. Try CurrencyConverter in one word. (I don't remember if you need to completely restart the project or if you only need to change the name.)

As for learning ObjC, remember that it is a (small) superset of C. So you need to know at least the basics of C first, or else it's not possible to fully understand ObjC.

There are many C intro books, My first contact with C once was through the O'Reilly book Practical C Programming, by Steve Oualline. It had many small examples that could be compiled directly on the command line. Much of the book isn't relevant for OS X programming (and can be skipped without problems), but I learned a good deal in a short while using this book.

Another practical intro book is C, A Software Engineering Approach. (Darnell/Margolis, Springer). I used this to refreshen my C knowledge not so long ago.

In any case, it's the fundamentals of C you need to know, like the language constructs itself, and some of it's strengths and weaknesses that comes from it being a "low-level" high-level language. C has many standard libraries that comes with it, but I don't think it's that important to fully master their use, since you'll be using the Cocoa frameworks anyway.

If/when you feel you know enough C, you can go ahead with ObjC and Cocoa. There are several ObjC/Cocoa books out there, my only personal experience is with Cocoa Programming, (Anguish et al., SAMS). This book takes great care explaining the ideas, philosopy, and conventions behind Cocoa, before the coding begins. I like this style, but if you want to dive in immediately with the programming, some of the newer O'Reilly books might be what you want. (I've heard that some of their older titles aren't that good.)

Another good option is the book by Aaron Hillegass, which generally got very good reviews. I haven't read it, and I don't know which approach it takes.

[sidecar71]

how about this error?

"warning: return type for ‘convertAmount:atRate:’ defaults to id"

the compiler points to the line:

"total = [converter convertAmount:amt atRate:rate];"

which calls:

------------
- (float) convertAmount:(float)amt atRate:(float)rate
{
return (amt * rate);
}
-----------

The method returns a float, which is what ‘total’ is, and 'amt' and 'rate' are both floats too. So what’s the problem? From what I can tell, everything is right.

[Chuckit]

Originally posted by sidecar71:
how about this error?

"warning: return type for ‘convertAmount:atRate:’ defaults to id"

the compiler points to the line:

"total = [converter convertAmount:amt atRate:rate];"

which calls:

------------
- (float) convertAmountfloat)amt atRatefloat)rate
{
return (amt * rate);
}
-----------

Does the file where the method is called import the interface file where it's declared?

[sidecar71]

Originally posted by Chuckit:
Does the file where the method is called import the interface file where it's declared?

Yes. I even tried to return an int, but it gives the same error. Maybe it's catching this error at a different location, but I dont know what I would to look for.

[Chuckit]

That's just odd. Maybe try cleaning the project? That's my first tack when anything weird is happening, and it works a good deal of the time.

[sidecar71]

Originally posted by Chuckit:
That's just odd. Maybe try cleaning the project? That's my first tack when anything weird is happening, and it works a good deal of the time.

Actually, something in these files were currupted, because when I went back in, project builder provided messages about not being able to read certain files. I could still use the current build, but I decided to scrap the whole thing and start again. It's an easy program, but I think there may have been confusion between "Currency Converter" and "CurrencyConverter", so I trashed ALL the files.

Thanks again for the help...