iphone sdk: drawing weird characters using custom fonts

I'm drawing custom fonts in a view but I'm having trouble to set correctly the map of characters. The thing is that I'm unable to draw some of the characters such as "ü", "ä", "á"... apparently because of differences between the encoding formats.

To make this simple I would want to know how I can store in a NSString a character corresponding to a position such as 0x00C9, 0x00D1 and so on. 开发者_开发问答Any idea?

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Have you tried [NSString stringWithUTF8String: ] ?