//异常捕捉
@try {
//有可能出错的代码
<#Code that can potentially throw an exception#>
}
@catch (NSException *exception) {
//错误的处理方法 一般用来打印错误星系
<#Handle an exception thrown in the @try block#>
}
@finally {
<#Code that gets executed whether or not an exception is thrown#>
}