37
00:02:26,000 --> 00:02:32,000
接下来，我们看下一个知识点，就是决策

38
00:02:32,000 --> 00:02:38,000
就是令牌的一种什么,

39
00:02:38,000 --> 00:02:42,000
一种分流,

40
00:02:42,000 --> 00:02:47,000
它走哪个流,

41
00:02:47,000 --> 00:02:52,000
决策点，一个入多个出,

42
00:02:52,000 --> 00:02:55,000
令牌流进来,

43
00:02:55,000 --> 00:03:00,000
然后在这里根据条件做分流

44
00:03:00,000 --> 00:03:03,000
符合条件走这边，不符合走这边

45
00:03:03,000 --> 00:03:06,000
当然可以多个，可以有条件1，条件2

46
00:03:06,000 --> 00:03:09,000
再加一个else

47
00:03:09,000 --> 00:03:11,000
这里只列了两个分支,

48
00:03:11,000 --> 00:03:14,000
也可以三个，多个分支，都可以,

49
00:03:14,000 --> 00:03:17,000
那么这些条件必须能够保证什么,

50
00:03:17,000 --> 00:03:24,000
有且只有一个出边上的条件为真,

51
00:03:24,000 --> 00:03:28,000
肯定要有一个，它令牌流出去

52
00:03:28,000 --> 00:03:30,000
而且只能有一个，不能多

53
00:03:30,000 --> 00:03:39,000
不能说这条也行，那条也行，那不行

54
00:03:39,000 --> 00:03:44,000
只有一个出边获得令牌

55
00:03:44,000 --> 00:03:46,000
比如说，像这个就类似于什么,

56
00:03:46,000 --> 00:03:50,000
用文本的代码的if条件

57
00:03:50,000 --> 00:03:56,000
A1，else A2，类似这样

58
00:03:56,000 --> 00:04:00,000
那么跟决策点对应的就是合并点

59
00:04:00,000 --> 00:04:02,000
你看，这个

60
00:04:02,000 --> 00:04:05,000
你看，这里是一进，这是入嘛

61
00:04:05,000 --> 00:04:08,000
这是出

62
00:04:08,000 --> 00:04:13,000
这个是入，入，这个一个出

63
00:04:13,000 --> 00:04:18,000
合并点就是多个入边，一个出边

64
00:04:18,000 --> 00:04:22,000
它的目的是把这个令牌

65
00:04:22,000 --> 00:04:29,000
重新收进来，变成这里出去的那个令牌

66
00:04:29,000 --> 00:04:31,000
那么把

67
00:04:31,000 --> 00:04:34,000
决策跟合并这两个菱形

68
00:04:34,000 --> 00:04:37,000
要成对匹配

69
00:04:37,000 --> 00:04:39,000
这是一个好习惯