Question

I am fairly new to a objective-c or in whole mac/iphone development. My question is how can I acces a data files(text files or flat files) in objective-c? For example I have a sample.txt file, how can I open this files and access its data? Do I need to use a class? And I heard about dictionary, is this term related to my problems?

Please kindly redirect me to a good site.

Thanks alot.

sasayins.

Answer 1

You can use regular fopen and fread to access the contents of a file. Alternatively, you can use NSString if your file contains only text or NSData for non-text data.

NSString *myString = [NSString stringWithContentsOfFile:@"/path/to/file"];

NSData *myData = [NSData dataWithContentsOfFile:@"/path/to/file"];

Edit

@"/path/to/file" a constant “Objective-C” style string. It is different to a regular C string (i.e. without the @ prepended) because it behaves like an object; you can send it messages, and it is able to be stored in NSArrays etc. From a Mac Programmer’s point of view, these Objective-C strings can be treated just like NSString objects.

The Mac OS X filesystem layout typically looks like this:

    /System          contains system files similar to C:\windows\
    /Library         contains libraries, similar to C:\windows\system32\
    /Users           similar to Windows' C:\Documents and Settings\
    /Applications    Mac's version of C:\Program Files\
    /Developer       Where Xcode, SDKs, and other developer tools live.

If your username on your Mac is “smith”, then your Home directory is /Users/smith. If you have a file in your Documents folder of your Home directory called data.txt, then you can use the following code to access it (but I wouldn’t recommend hard-coding paths like this)

NSString *myString = [NSString stringWithContentsOfFile:@"/Users/smith/Documents/data.txt"];

There are various functions available for reliably obtaining your home directory and other directories of particular interest. The NSString documentation explains the various methods available for manipulating strings containing paths.