让数字保持两位数格式

NSLog(@"%02ld",2);  
NSLog(@"%0.2f",0.2656);  
NSLog(@"%0.2f",0.2646);  
 
 
注意的是%0.2f 是会对数字进行一个四舍五入
 
2016-06-20 14:57:28.506 App[4010:98217] 02  
2016-06-20 14:57:28.507 App[4010:98217] 0.27  
2016-06-20 14:57:28.507 App[4010:98217] 0.26