1 00:00:02,050 --> 00:00:04,760 So by now, we already refactored a lot. 2 00:00:04,760 --> 00:00:06,360 I'm fully aware of that. 3 00:00:06,360 --> 00:00:08,990 But this is how you do write clean code. 4 00:00:08,990 --> 00:00:11,260 It's a step-by-step process, 5 00:00:11,260 --> 00:00:14,150 which is why I'm showing it in great detail here. 6 00:00:14,150 --> 00:00:16,160 Because that is what you will do ultimately, 7 00:00:16,160 --> 00:00:18,290 when you clean up your own code. 8 00:00:18,290 --> 00:00:21,140 It's about trying out things, being creative, 9 00:00:21,140 --> 00:00:23,530 and moving things around. 10 00:00:23,530 --> 00:00:26,350 And speaking of moving things around, 11 00:00:26,350 --> 00:00:29,470 we now use errors, which is great. 12 00:00:29,470 --> 00:00:32,650 But now we have all that code for creating errors 13 00:00:32,650 --> 00:00:35,470 side by side with code that, for example, 14 00:00:35,470 --> 00:00:38,070 dispatches different process functions 15 00:00:38,070 --> 00:00:40,113 for different transaction methods. 16 00:00:41,410 --> 00:00:45,063 This, again, is mixing different levels of abstraction. 17 00:00:46,890 --> 00:00:49,910 So we should consider splitting our functions. 18 00:00:49,910 --> 00:00:52,840 For example, here in process transactions, 19 00:00:52,840 --> 00:00:56,250 where I check for whether my transactions are empty 20 00:00:56,250 --> 00:00:57,823 to then create an error, 21 00:00:58,890 --> 00:01:00,630 we can create a new function, 22 00:01:00,630 --> 00:01:02,730 which we could name "validateTransactions" 23 00:01:04,730 --> 00:01:07,580 where we get all the transactions. 24 00:01:07,580 --> 00:01:09,450 And then we move this code 25 00:01:09,450 --> 00:01:12,603 where we generate this error into this function. 26 00:01:14,400 --> 00:01:17,767 Then here in process transactions, we can simply call 27 00:01:17,767 --> 00:01:22,240 validateTransactions before we go through this for loop. 28 00:01:22,240 --> 00:01:24,030 The great advantage of this approach 29 00:01:24,030 --> 00:01:28,590 is not just that processTransactions is now slimmer, 30 00:01:28,590 --> 00:01:30,810 though we should forward transactions 31 00:01:30,810 --> 00:01:33,510 to validate transactions function, 32 00:01:33,510 --> 00:01:36,700 but although that because we use real errors, 33 00:01:36,700 --> 00:01:38,460 and we throw this error, 34 00:01:38,460 --> 00:01:41,760 we use a built-in mechanism in the programming language, 35 00:01:41,760 --> 00:01:44,602 which will ensure that this automatically bubbles up. 36 00:01:44,602 --> 00:01:48,380 So it will just bubble through processTransactions, 37 00:01:48,380 --> 00:01:50,404 canceling this function as well, 38 00:01:50,404 --> 00:01:54,610 if an error is generated inside of validateTransactions, 39 00:01:54,610 --> 00:01:58,550 moving up to the next function until it is being handled, 40 00:01:58,550 --> 00:02:00,600 which in this case, it is here. 41 00:02:00,600 --> 00:02:03,550 And this of course, is great. 42 00:02:03,550 --> 00:02:06,380 This here, of course, should be transactions, by the way, 43 00:02:06,380 --> 00:02:07,953 not transaction. 44 00:02:09,330 --> 00:02:10,400 Now, we could argue 45 00:02:10,400 --> 00:02:13,140 that we have mixed levels of abstraction here. 46 00:02:13,140 --> 00:02:16,290 Calling is empty, and then this low level code 47 00:02:16,290 --> 00:02:18,820 of creating the error and adding a code, 48 00:02:18,820 --> 00:02:21,620 and therefore, we could also add another function here, 49 00:02:21,620 --> 00:02:23,710 where we build this error. 50 00:02:23,710 --> 00:02:27,330 You could absolutely do that but I will not do it here. 51 00:02:27,330 --> 00:02:29,110 I think it's too much splitting, 52 00:02:29,110 --> 00:02:31,600 and if you would want such a helper function 53 00:02:31,600 --> 00:02:34,080 which builds an error, I would recommend 54 00:02:34,080 --> 00:02:36,600 that you simply create your own error class, 55 00:02:36,600 --> 00:02:38,240 which you instantiate here. 56 00:02:38,240 --> 00:02:40,290 So I will leave it like this. 57 00:02:40,290 --> 00:02:42,790 Nonetheless, we have some extractions left to do 58 00:02:42,790 --> 00:02:46,137 here for processTransaction. 59 00:02:46,137 --> 00:02:47,860 There we check whether it's not open, 60 00:02:47,860 --> 00:02:50,580 or if it's neither a payment nor a refund. 61 00:02:50,580 --> 00:02:53,573 And we can outsource these validations as well. 62 00:02:55,370 --> 00:02:59,030 So we can add a new function here, 63 00:02:59,030 --> 00:03:02,920 which we name "validateTransaction", for example, 64 00:03:02,920 --> 00:03:05,353 receiving the transaction as a parameter. 65 00:03:06,550 --> 00:03:07,830 And now we could either create 66 00:03:07,830 --> 00:03:10,040 one function for each check here 67 00:03:10,040 --> 00:03:14,400 or we take both checks and put them into the same function. 68 00:03:14,400 --> 00:03:15,470 Which I will do here 69 00:03:15,470 --> 00:03:17,600 because we're doing the same kind of work, 70 00:03:17,600 --> 00:03:21,000 we're validating a transaction, just with different checks, 71 00:03:21,000 --> 00:03:22,740 and therefore having this in one function 72 00:03:22,740 --> 00:03:24,910 makes a lot of sense to me. 73 00:03:24,910 --> 00:03:29,610 And now we can just call validate transaction here 74 00:03:30,670 --> 00:03:34,680 before we then try to process the different transactions. 75 00:03:34,680 --> 00:03:38,850 And again, because validateTransaction froze an error, 76 00:03:38,850 --> 00:03:41,990 if we got an error, this processTransaction, 77 00:03:41,990 --> 00:03:45,250 function execution will be canceled if an error occurs, 78 00:03:45,250 --> 00:03:47,510 and this code will not be executed. 79 00:03:47,510 --> 00:03:50,380 Instead, we move up to the next function above it 80 00:03:50,380 --> 00:03:52,360 until this is being handled, 81 00:03:52,360 --> 00:03:56,173 which in this case is happening here in this for loop. 82 00:03:57,500 --> 00:04:00,420 And that now again, we're more extractions, 83 00:04:00,420 --> 00:04:03,820 which hopefully, overall, help with readability 84 00:04:03,820 --> 00:04:07,733 if you would read this entire code top to bottom.