402
00:17:30,860 --> 00:17:34,610
那首先要说在前面的，就是说

403
00:17:36,590 --> 00:17:39,770
这个状态机实际上已经是一种

404
00:17:42,060 --> 00:17:45,320
描述行为上的差别了

405
00:17:45,820 --> 00:17:47,860
就是说，实际上它是说什么

406
00:17:48,140 --> 00:17:49,140
一个

407
00:17:49,420 --> 00:17:51,110
事件进来

408
00:17:51,390 --> 00:17:56,890
对吧，然后最终你是执行了哪些action，输出就是action嘛

409
00:17:57,170 --> 00:17:59,450
哪些action是你要做的

410
00:17:59,970 --> 00:18:00,630

411
00:18:03,500 --> 00:18:04,450
也就是说

412
00:18:05,150 --> 00:18:06,540
它的区别

413
00:18:06,930 --> 00:18:09,350
为什么要通过状态机来判断

414
00:18:09,350 --> 00:18:11,570
因为这个action1，action2

415
00:18:12,120 --> 00:18:13,770
action3等等

416
00:18:14,170 --> 00:18:15,520
是不一样的

417
00:18:19,380 --> 00:18:21,460
那么这已经是一种

418
00:18:21,780 --> 00:18:24,260
行为上的差别

419
00:18:25,590 --> 00:18:28,040
就是把差别写在行为里面

420
00:18:28,380 --> 00:18:30,512
那我们在第八章的时候

421
00:18:30,512 --> 00:18:31,364
软件方法

422
00:18:31,364 --> 00:18:33,710
第八章的时候已经说了

423
00:18:35,230 --> 00:18:41,932
这张幻灯片就是从分析设计高阶那个裁过来的

424
00:18:41,932 --> 00:18:43,050
截过来的

425
00:18:44,860 --> 00:18:46,360
说类图的时候

426
00:18:46,850 --> 00:18:48,010
的幻灯片

427
00:18:48,490 --> 00:18:50,960
如果能通过

428
00:18:52,170 --> 00:18:53,550
属性值的差别

429
00:18:53,550 --> 00:18:55,850
也就是说，通过关联

430
00:18:56,920 --> 00:18:58,640
来显式建模的

431
00:19:00,810 --> 00:19:02,767
那就尽量变成关联

432
00:19:02,767 --> 00:19:05,160
包括属性也是一种关联

433
00:19:07,230 --> 00:19:07,980
那实际上

434
00:19:07,980 --> 00:19:08,730
就是

435
00:19:10,020 --> 00:19:11,875
在类图那个地方也说过

436
00:19:11,875 --> 00:19:13,730
就是说，实际上就是一种

437
00:19:14,100 --> 00:19:16,230
设计模式里面说的那个

438
00:19:16,840 --> 00:19:19,030
组合优于继承

439
00:19:21,780 --> 00:19:22,640
那个

440
00:19:23,290 --> 00:19:23,592

441
00:19:23,592 --> 00:19:24,500
就是说

442
00:19:24,780 --> 00:19:26,300
属性的差别

443
00:19:26,970 --> 00:19:28,309
能解决的

444
00:19:28,309 --> 00:19:32,060
就不要拖到行为上的差别

445
00:19:36,930 --> 00:19:41,707
当然，像设计模式里面说什么组合优于继承

446
00:19:41,707 --> 00:19:45,447
它本质上并没有解决这个行为差别的问题

447
00:19:45,447 --> 00:19:47,108
只是把它推迟了

448
00:19:47,108 --> 00:19:50,224
比如说，变成一个什么策略模式

449
00:19:50,224 --> 00:19:52,509
但实际上后面还是泛化

450
00:19:52,509 --> 00:19:57,080
行为差别还是在策略模式那里面写代码

451
00:19:57,360 --> 00:19:59,749
没有把背后的道理

452
00:19:59,749 --> 00:20:01,900
变成属性的差别

453
00:20:04,090 --> 00:20:07,190
所以我们在第八章的时候也说了嘛

454
00:20:07,190 --> 00:20:08,170
很多那个什么

455
00:20:09,170 --> 00:20:10,192
设计模式

456
00:20:10,192 --> 00:20:12,646
策略模式什么的

457
00:20:12,646 --> 00:20:15,918
表面上好像做了事情，当然也有改善

458
00:20:15,918 --> 00:20:17,350
可以随机的

459
00:20:17,660 --> 00:20:19,116
随时切换策略

460
00:20:19,116 --> 00:20:19,480
对吧

461
00:20:19,480 --> 00:20:21,848
通过把策略分离出去

462
00:20:21,848 --> 00:20:22,576
随时切换

463
00:20:22,576 --> 00:20:23,669
但是还是什么

464
00:20:23,669 --> 00:20:25,490
实际上还是面向过程的

465
00:20:29,330 --> 00:20:31,418
还是在行为上的差别

466
00:20:31,418 --> 00:20:33,090
并没有本质的变化

467
00:20:33,560 --> 00:20:36,420
那属性值差别就像这个了

468
00:20:36,860 --> 00:20:37,505
人

469
00:20:37,505 --> 00:20:40,730
假设我要有一个计税的

470
00:20:41,440 --> 00:20:42,660
一个行为

471
00:20:43,820 --> 00:20:44,938
那个行为的话

472
00:20:44,938 --> 00:20:46,430
它是跟收入有关的

473
00:20:49,430 --> 00:20:52,881
男人的话可能是收入乘

474
00:20:52,881 --> 00:20:55,100
0.1，10%

475
00:20:55,550 --> 00:20:58,170
女人的话，9%，0.09

476
00:20:59,230 --> 00:21:00,416
那有两种做法

477
00:21:00,416 --> 00:21:01,800
一个是泛化了

478
00:21:01,800 --> 00:21:02,789
男人，计税

479
00:21:02,789 --> 00:21:03,580
然后

480
00:21:03,580 --> 00:21:05,360
0.1，这个，0.09

481
00:21:06,370 --> 00:21:08,453
就是写在代码里面了

482
00:21:08,453 --> 00:21:09,703
在这里有区别

483
00:21:09,703 --> 00:21:11,370
但显然这是不好的

484
00:21:11,370 --> 00:21:13,246
你看这0.1,0.09

485
00:21:13,246 --> 00:21:13,454

486
00:21:13,454 --> 00:21:14,913
这是一个硬编码

487
00:21:14,913 --> 00:21:15,330
对吧

488
00:21:21,360 --> 00:21:23,110
那我们把它变成概念

489
00:21:25,070 --> 00:21:26,290
把硬编码

490
00:21:27,090 --> 00:21:28,527
拿出来，变成概念

491
00:21:28,527 --> 00:21:29,605
这个是什么

492
00:21:29,605 --> 00:21:30,323
是税率嘛

493
00:21:30,323 --> 00:21:31,761
跟性别相关的税率

494
00:21:31,761 --> 00:21:32,300
对不对

495
00:21:33,250 --> 00:21:34,860
人有性别

496
00:21:34,860 --> 00:21:36,930
每个性别有一个税率

497
00:21:36,930 --> 00:21:38,310
那代码怎么写

498
00:21:38,310 --> 00:21:41,760
就是税费等于收入乘以性别的税率

499
00:21:42,870 --> 00:21:45,467
通过这些组合就可以计算出来

500
00:21:45,467 --> 00:21:46,580
就是通过这个

501
00:21:47,290 --> 00:21:48,480
这些运算

502
00:21:49,370 --> 00:21:50,570
就可以把它

503
00:21:51,580 --> 00:21:52,780
运算出来

504
00:21:54,230 --> 00:21:55,056
就不用泛化

505
00:21:55,056 --> 00:21:58,030
也不用什么if else

506
00:21:59,440 --> 00:22:00,760
也就是说

507
00:22:03,500 --> 00:22:06,649
能在属性这个级别上解决的

508
00:22:06,649 --> 00:22:08,830
就在属性级别上解决

509
00:22:10,250 --> 00:22:11,600
实在不行了

510
00:22:11,600 --> 00:22:14,300
在行为这个层面上解决

511
00:22:15,420 --> 00:22:19,300
那状态已经是行为解决的一种方式了

512
00:22:23,920 --> 00:22:26,380
那如果在行为上解决的话

513
00:22:27,310 --> 00:22:29,460
有这么几种方式嘛

514
00:22:30,000 --> 00:22:32,640
来表达行为上差别

515
00:22:33,730 --> 00:22:36,090
比如说，条件分支

516
00:22:36,960 --> 00:22:39,740
if else或switch case都行

517
00:22:41,380 --> 00:22:44,000
如果仅仅是一个条件

518
00:22:45,670 --> 00:22:47,260
那这个问题不大

519
00:22:49,810 --> 00:22:51,670
但是往往是什么

520
00:22:51,670 --> 00:22:54,328
我们的系统之所以复杂

521
00:22:54,328 --> 00:22:54,860
就是

522
00:22:55,320 --> 00:22:58,170
如果你用条件分支来解决的话

523
00:22:58,950 --> 00:23:00,460
它很可能是

524
00:23:00,920 --> 00:23:02,030
多个嵌套

525
00:23:02,310 --> 00:23:04,568
要么是多层嵌套

526
00:23:04,568 --> 00:23:05,070
if

527
00:23:07,450 --> 00:23:07,748

528
00:23:07,748 --> 00:23:08,644
然后呢

529
00:23:08,644 --> 00:23:11,930
else，else下面还可以加if

530
00:23:13,380 --> 00:23:13,609

531
00:23:13,609 --> 00:23:17,740
然后在else下面还可以再if，多层嵌套的

532
00:23:20,550 --> 00:23:22,180
比如说，像右边这个

533
00:23:22,960 --> 00:23:26,481
它这个变量倒是简单，就一个

534
00:23:26,481 --> 00:23:31,010
这就是一个典型的面试题嘛

535
00:23:31,500 --> 00:23:33,240
3的时候，输出什么

536
00:23:33,240 --> 00:23:34,980
5的时候，输出什么,

537
00:23:35,260 --> 00:23:36,920
但是你看它这个

538
00:23:37,390 --> 00:23:40,000
首先，你要判断

539
00:23:41,100 --> 00:23:43,500
3而且是5

540
00:23:44,000 --> 00:23:46,934
如果这个表达式

541
00:23:46,934 --> 00:23:47,260
是

542
00:23:48,130 --> 00:23:49,190
假的

543
00:23:49,840 --> 00:23:51,570
那就有两种可能嘛

544
00:23:51,570 --> 00:23:52,220
要么是

545
00:23:53,530 --> 00:23:53,712

546
00:23:53,712 --> 00:23:55,358
就有三种可能

547
00:23:55,358 --> 00:23:56,455
要么不是3

548
00:23:56,455 --> 00:23:57,370
要么不是5

549
00:23:57,370 --> 00:23:58,650
要么两个都不是

550
00:23:58,930 --> 00:23:59,547
对吧

551
00:23:59,547 --> 00:24:01,400
而每种的话

552
00:24:02,710 --> 00:24:04,710
输出都是不一样的

553
00:24:11,120 --> 00:24:12,180
那这个

554
00:24:13,710 --> 00:24:14,490
就是

555
00:24:15,310 --> 00:24:16,400
多个的

556
00:24:16,680 --> 00:24:17,370

557
00:24:17,970 --> 00:24:20,130
条件，嵌套的条件

558
00:24:21,730 --> 00:24:23,450
那更复杂的就是

559
00:24:23,730 --> 00:24:25,863
如果它是多个变量的呢

560
00:24:25,863 --> 00:24:26,290
对吧