using plist in iphone programming

I've read up Apple's documentation of plist: http://developer.apple.com/library/mac/documentation/cocoa/Conceptual/PropertyLists/PropertyLists.pdf

However I've got a few questions about it:

1) When we use the [dict writeToFile:pli开发者_开发百科stPath atomically:YES] API, does it overwrite the current content of the plist? It doesn't say anything in the documentation.

2) Are we supposed to actually make the plist manually in Xcode by new file->resources->property list? Or are we supposed to have this:

NSFileManager *fileManager = [NSFileManager defaultManager];
NSData *xmlData = [NSPropertyListSerialization  //... a very long line here

if([fileManager fileExistsAtPath:plistPath]) {
    [xmlData writeToFile:plistPath atomically:YES];
}    
else {
    [fileManager createFileAtPath:plistPath contents:xmlData attributes:nil];
}

3) How do we check if we've actually written data to property list? I tried products -> myapp.app -> "reveal in finder" -> right click -> show package contents, and there are some plists there, but I can't see the data being written! Is that mean I'm failed writing data to plist?

EDIT: Thanks everyone! Sorry for being silly today!

From the description of writeToFile:atomically:

If flag is YES, the dictionary is written to an auxiliary file, and then the auxiliary file is renamed to path. If flag is NO, the dictionary is written directly to path. The YES option guarantees that path, if it exists at all, won’t be corrupted even if the system should crash during writing.

Since it is written to an auxiliary file and then renamed to the specified path, I would assume that it overwrites the current content of the file.

You should use the NSFileManager to find the application's documents directory and write the plist there. You should not use a resource, as you are going to write to it during the course of executing the app.

Add some logging (e.g., NSLog(@"plist path: %@", plistPath);) to show where the plist is getting written.

1) It will overwrite the current content. If you want to append some more data to your current plist file, first read it to a dictionary and add the data and write it back. 2) You can add it manually or create it programmatically. 3) Just log the contents of the plist file after writing.