Problems with using xcode (IOS)

1. Code sign error: the identity 'iphone developer 'doesn' t match any valid, non-expired certificate/private key pair in your Keychains

At first, I thought it was wrong to set the Code Sign. After searching for the Internet for a long time, I tried all kinds of methods without any effect. In the end, I restarted my computer in a rage, and then I was puzzled. Me X! I bought a table last year!

I personally think it is a valuable reference:

Http://stackoverflow.com/questions/9949700/iphone-developer-doesnt-match-any-valid-non-expired-certificate-private-key-p/9950273#9950273

Http://stackoverflow.com/questions/11869486/how-can-i-solve-the-code-sign-error-the-identity-ipad-doesnt-match-any-valid

2. simple application of GPS on iOS platform (obtain longitude and latitude and detailed address)

-(Void) reversegeocoder :( mkreversegeocoder *) geocoder didfindplacemark :( mkplacemark *) placemark

The placemark obtained by using the above method may be a null value in the member variable. You can only make a non-empty judgment before using it.

Summary:

1. Do not count on the rigor of the code written by others. Be sure to protect yourself.

2. The placemark member uses null values. In my personal opinion, it can reduce unnecessary memory usage and overhead for creating string objects. In the future, you can also use this initialization method for your code.

3.

Common xcode4 shortcut keys

4. Convert the long type to a string:

Long long testlong= 999999;

Char stingtest [32];

Sprintf (stringtest, "%LlD ", testlong );

That is, the two l are in front of D and cannot be found online. Ask the student to know.