1 00:00:02,160 --> 00:00:04,800 Now, the number of parameters matter 2 00:00:04,800 --> 00:00:08,850 but in addition, it's also the kind of parameters. 3 00:00:08,850 --> 00:00:11,520 And there's one specific kind of parameter, 4 00:00:11,520 --> 00:00:13,550 which you absolutely wanna avoid 5 00:00:13,550 --> 00:00:17,580 and that would be the output parameter. 6 00:00:17,580 --> 00:00:20,420 Now, you should try to avoid output parameters 7 00:00:20,420 --> 00:00:25,070 or output arguments, especially if they are unexpected. 8 00:00:25,070 --> 00:00:27,610 And I have this second part here 9 00:00:27,610 --> 00:00:30,440 because in some cases, especially when working 10 00:00:30,440 --> 00:00:33,490 with certain third-party libraries or frameworks, 11 00:00:33,490 --> 00:00:35,220 you can't avoid them. 12 00:00:35,220 --> 00:00:38,040 But they should never be unexpected. 13 00:00:38,040 --> 00:00:39,930 Take this as an example. 14 00:00:39,930 --> 00:00:41,890 We have a function, which we call, 15 00:00:41,890 --> 00:00:43,040 which is named createId 16 00:00:44,037 --> 00:00:45,436 and which takes a user. 17 00:00:45,436 --> 00:00:49,210 Now, let's assume that this function internally 18 00:00:49,210 --> 00:00:52,050 then adds an ID field 19 00:00:52,050 --> 00:00:55,700 to that user object which it receives as an input. 20 00:00:55,700 --> 00:00:57,300 And that would be not great 21 00:00:57,300 --> 00:01:00,840 because then the user, which is passed into the function, 22 00:01:00,840 --> 00:01:03,290 gets modified by the function. 23 00:01:03,290 --> 00:01:05,950 So the function doesn't return the ID 24 00:01:05,950 --> 00:01:08,180 for the user, which was passed in. 25 00:01:08,180 --> 00:01:11,090 Instead, it manipulates the user object, 26 00:01:11,090 --> 00:01:12,480 which it received. 27 00:01:12,480 --> 00:01:14,640 Here's the full example in code. 28 00:01:14,640 --> 00:01:16,370 It's a createId function 29 00:01:16,370 --> 00:01:19,100 and internally, it manipulates the value 30 00:01:19,100 --> 00:01:23,420 which it receives and adds an id field with a certain value. 31 00:01:23,420 --> 00:01:26,120 So if you pass user to createId, 32 00:01:26,120 --> 00:01:28,460 it simply will have that id thereafter 33 00:01:28,460 --> 00:01:31,300 and this is not necessarily obvious. 34 00:01:31,300 --> 00:01:34,880 We might not expect the user to be edited. 35 00:01:34,880 --> 00:01:38,480 We might have expected that we can simply call createId 36 00:01:38,480 --> 00:01:41,250 and get back an id which we store in a constant 37 00:01:41,250 --> 00:01:43,370 but that's not what this function is doing 38 00:01:43,370 --> 00:01:46,520 and therefore, this is not really clean code. 39 00:01:46,520 --> 00:01:48,680 It has a output parameter 40 00:01:48,680 --> 00:01:52,900 because it actually outputs the results of its work, 41 00:01:52,900 --> 00:01:55,360 in this case, generating the id 42 00:01:55,360 --> 00:01:58,110 as part of the parameter which it received. 43 00:01:58,110 --> 00:01:59,960 It manipulates the parameter 44 00:01:59,960 --> 00:02:02,750 instead of returning a new value. 45 00:02:02,750 --> 00:02:04,890 You generally wanna avoid this 46 00:02:04,890 --> 00:02:07,720 and you especially wanna avoid having functions, 47 00:02:07,720 --> 00:02:11,430 which don't sound like they're doing what they are doing. 48 00:02:11,430 --> 00:02:15,680 It might be better if your function would be named addId 49 00:02:15,680 --> 00:02:17,751 instead of createId. 50 00:02:17,751 --> 00:02:21,830 So let's say it still does what it does internally 51 00:02:21,830 --> 00:02:25,270 but now, the name addId makes it more obvious 52 00:02:25,270 --> 00:02:28,830 that it adds an ID to the user, which we pass in. 53 00:02:28,830 --> 00:02:31,060 It doesn't just create an ID 54 00:02:31,060 --> 00:02:33,430 where we then could reasonably expect 55 00:02:33,430 --> 00:02:36,030 that the ID's returned but instead, 56 00:02:36,030 --> 00:02:37,130 addId makes it very obvious 57 00:02:37,130 --> 00:02:39,807 that the user is likely to be edited. 58 00:02:39,807 --> 00:02:42,630 Hence here, we still have an output parameter 59 00:02:42,630 --> 00:02:44,560 but at least it's more expected. 60 00:02:44,560 --> 00:02:46,269 So it would be okay. 61 00:02:46,269 --> 00:02:48,140 It still might be even cleaner 62 00:02:48,140 --> 00:02:51,130 to not use output parameters in the first place 63 00:02:51,130 --> 00:02:53,450 but if you can't do it any other way, 64 00:02:53,450 --> 00:02:55,270 then at least make it obvious 65 00:02:55,270 --> 00:02:57,938 that you do have an output parameter. 66 00:02:57,938 --> 00:03:00,690 Now, an even cleaner solution, by the way, 67 00:03:00,690 --> 00:03:03,680 might be to use an object-oriented approach 68 00:03:03,680 --> 00:03:05,450 where you have a user object 69 00:03:05,450 --> 00:03:08,316 on which you call addId without any arguments. 70 00:03:08,316 --> 00:03:10,930 Then this would be very obvious 71 00:03:10,930 --> 00:03:14,240 that this probably edits the existing user 72 00:03:14,240 --> 00:03:16,670 and here, it would therefore not be unexpected. 73 00:03:16,670 --> 00:03:19,990 After all, here we don't even have a parameter, 74 00:03:19,990 --> 00:03:23,130 so we definitely also don't have an output parameter 75 00:03:23,130 --> 00:03:25,370 in here because there is no parameter at all. 76 00:03:25,370 --> 00:03:27,980 So this function is totally understandable 77 00:03:27,980 --> 00:03:30,390 and doesn't do anything strange things. 78 00:03:30,390 --> 00:03:33,230 Here's a full pseudo example in code. 79 00:03:33,230 --> 00:03:36,060 We have the User class with the addId method 80 00:03:36,060 --> 00:03:39,280 and here, we don't have any unexpected behavior. 81 00:03:39,280 --> 00:03:40,790 Instead here, it's pretty clear 82 00:03:40,790 --> 00:03:43,963 what this method does to the customer object here. 83 00:03:45,190 --> 00:03:47,500 And therefore, long story short, 84 00:03:47,500 --> 00:03:51,720 the best case is to avoid output arguments, if possible. 85 00:03:51,720 --> 00:03:53,160 But if you need them, 86 00:03:53,160 --> 00:03:55,290 do it as we showed it here in the middle 87 00:03:55,290 --> 00:03:57,590 with a clearly named function 88 00:03:57,590 --> 00:03:59,620 and avoid having function names 89 00:03:59,620 --> 00:04:02,000 which don't make it clear what you're doing 90 00:04:02,000 --> 00:04:03,320 inside of the function 91 00:04:03,320 --> 00:04:06,790 because output parameters can be super confusing 92 00:04:06,790 --> 00:04:08,380 and lead to bugs. 93 00:04:08,380 --> 00:04:11,350 I mean, after all, you are editing a value 94 00:04:11,350 --> 00:04:13,290 which was passed into a function 95 00:04:13,290 --> 00:04:16,280 and that's generally not something you expect 96 00:04:16,280 --> 00:04:17,343 from a function.