oc中使用switch实现图片浏览功能

 1 -(void)turnPage:(BOOL)isUp{
 2     if(isUp){
 3         self.currentNum++;
 4     }else{
 5         self.currentNum--;
 6     }
 7     switch (self.currentNum) {
 8         case 0:
 9             //"上一页"失效
10             self.lastButton.enabled = NO;
11             break;
12         case 1:
13             //打开失效的“上一页”
14             self.lastButton.enabled = YES;
15             break;
16         case QUESTION_NUM-2:
17             //打开失效的“下一页”
18             self.nextButton.enabled = YES;
19             break;
20         case QUESTION_NUM-1:
21             //"下一页"失效
22             self.nextButton.enabled = NO;
23             break;     
24         default:
25             break;
26     }
27     self.currentDictionary = [self.questionArray objectAtIndex:self.currentNum];
28     //重新设置UI
29     [self setUI]; 
30 }