ios developed to retrieve data from the network connected to the Internet to catch the exception if there is no problem, items urgently!

Now I get the data from the Web, but you must consider the circumstances of the current user is not networked, in order to avoid downtime or quit unexpectedly appear, must catch this exception, I do not know iphone development expert who can provide a complete section of code, brother just learning objc, a rookie, do not be afraid to say too simple to write. Thank you! ! There is also a problem, in order to improve the user experience when networking is necessary to display a dialog box waiting (class of the progress bar), I do not know how to achieve this, it troublesome piece of code to the younger grateful ah, before brother had been In doing android development, now transplanted to ios, project reminders tight grip, so I hope to get ios cattle guidance ah! !
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Network connection can use ASIHTTPRequest , which will return an error various abnormal to you, you can handle yourself. Wait for Hot Wheels can MBProgressHUD . Both are open source, the use of very wide.
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cited a floor reply:

network connection can use ASIHTTPRequest, which will return an error various abnormal to you, you can handle yourself. Wait for Hot Wheels can MBProgressHUD. Both are open source, the use of very wide.

What can specifically point code brother beginner to novice. Seek guidance ah
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A big push on the network information, and links to the inside of my Demo's always been there.
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The official demo for detecting network demo
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reference to the third floor of the reply:

a big push on

network information, and links to the inside of my Demo's always been there.

Oh really good information thanks ah!