Branch fixes delete training 2 #93
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yejiadong
approved these changes
Oct 14, 2020
| return studentsList.stream() | ||
| .filter(student -> student.getId().equals(id)) | ||
| .findFirst() | ||
| .get(); |
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if studentsList empty, is it safe that .get() will not throw a null pointer error?
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It's assumed here that there will always be the Id existing in the list, is there a scenario that this wont happen?
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makes sense, but might be good to include an assertion here in case of code changes in future
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yep thanks, shall do that. We see how this find by id goes, best is we abstract it to a util method
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IMPORTANT: Search student by Id
Given how tricky it is to maintain immutable student objects in an implicitly mutable manner (we modify a lot of stuff) and especially how the "same" student is being contained in both student list and INDIVIDUAL training, going forward, we should point to students using Id values instead of equality checks.
A True Story Example - Major bug
ts-add 1 1ts-add 2 1delete-training 1a. Loop through all students within T1 training list of students
b. Remove T1's date time from that student's training schedule
c. Update the
Modelusingmodel.setStudent(oldStudent, newStudent)There will be a
StudentNotFoundExceptionfor 4c because:.equals()will be false ==> Student not foundT1 stores the older Alex object and will not match any other newer Alex object IF we use
.equals().Hence, the next best thing we can use is
Idwhich was created to be unique and immutable.The bug above has been fixed.