- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSString * str = @"asfawre";
// 2015-12-15 10:24:56.828 试炼[868:24347] 7
// 2015-12-15 10:24:56.829 试炼[868:24347] awre
// 2015-12-15 10:24:56.829 试炼[868:24347] asf
// 2015-12-15 10:24:56.829 试炼[868:24347] faw
NSLog(@"%lu",str.length);
NSLog(@"%@",[str substringFromIndex:3]);
NSLog(@"%@",[str substringToIndex:3]);
NSLog(@"%@",[str substringWithRange:NSMakeRange(2, 3)]);
}
