IPhone : How to get the proper iOS version programmatically?

I want to get the current os version of user device for some analysis in backend. Im trying to get it as below,

[[[UIDevice currentDevice] systemVersion] floatValue]; **//not returning the minor version number**

When I test this by running in my iPhone which is having iOS 8.0.2, this api returns me 8.000000 as the result but I need the exact iOS version which is 8.0.2

Any help in fixing this problem is appreciated in advance.