BOOL isTheObjectThere = [myArray containsObject: @"my string"];

或者如果您需要知道它在哪里

or if you need to know where it is

NSUInteger indexOfTheObject = [myArray indexOfObject: @"my string"];

我强烈建议您阅读 关于 NSArray 的文档.***在发布您的问题之前这样做:-)

I strongly recommend you read the documentation on NSArray. It's best to do that before posting your question :-)