restrictions on fields?

[wispy matrix]

When it comes to setting values of field of an object, it could either be done via constructor or using getters/setters. I'm thinking is there a more preferred way or it doesn't matter what we do? Suppose i don't want the fields to be negative. How should i go about it?

[iron surge]

<@&987246399047479336> please have a look, thanks.

[iron surge]

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[mossy dawn]

well, it obviously always depends on the exact situation. like, suppose there is a game and it has a stop() method, which eventually will set a field isRunning to false.
i wouldnt call this a setter method, yet it modifies a field.

but if ur thinking about classic "data classes", such as a Person with name and age, constructor and setters are just the most natural thing to have

although, in general, u would prefer immutable classes. so no setters, just the constructor

that said, validation should be made whenever u modify it

so constructor and setter

to avoid duplication, u can let the constructor use the setter

and then only have the validation in latter

[wispy matrix]

ok so constructor is more for default values and things, but when modifying we should do the validation in setter

i don't often see code where they use setters in constructor usually or maybe i saw bad code, is it always recommended to use setters in constructor to avoid duplication? or would that depend on use case

so it would be something like this

[mossy dawn]

duplication is almost always bad

if u duplicate the check in setter and constructor, thats bad

btw, those checks are kinda bad

validation at this point is supposed to throw

and not defensively say "u did a mistake" and then continue

this should have happened before that point already

attempting to call a setter with wrong values is incorrect usage and should result in an exception

that said, u already have duplication here

of the pattern "if < 0 ... no negative allowed"

so id create a method

requirePositive(length);

[wispy matrix]

like this?

[mossy dawn]

IllegalArgumentException is the idiomatic exception

[wispy matrix]

oh lol i forgot the name but yea that one

[mossy dawn]

also, u should provide the current value in the exception

otherwise its hard to debug

private static void requirePositive(int x) {
  if (x < 0) {
    throw new IllegalArgumentException("Must not be negative, but was: " + x);
  }
}

[wispy matrix]

oh

now i can use this method in my setters

or anywhere i'd like a positive value

this is much better, thanks

i see how constructors are valuable when it comes to immutable classes