ios7以前是这样的：
nsstring * nsstringtoopen = [nsstring stringwithformat: @itms-apps://ax.itunes.apple.com/webobjects/mzstore.woa/wa/viewcontentsuserreviews?type=purple+software&id=%@,nsappid ]; [[uiapplication sharedapplication] openurl:[nsurl urlwithstring:nsstringtoopen]]; ios8以后那样是没有反应的，只能这样才行
找到应用程序的描述链接，比如：http://itunes.apple.com/gb/app/yi-dong-cai-bian/id391945719?mt=8
[[uiapplication sharedapplication] openurl:[nsurl urlwithstring:@itms://itunes.apple.com/gb/app/yi-dong-cai-bian/id391945719?mt=8]];