Extract the text between the two substring in NSString

I need to extract the all the lines between two strings like开发者_如何学编程 Begin and End in the NSString.

For example,

<some text>
Begin
line1
line2
End
<some Text>
Begin
line1
line2
End

I need to discard all the text that is not coming under these blocks. Any idea how to do this?

See -componentsSeparatedByString: in the NSString documentation.