this post was submitted on 07 Sep 2024
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Totally agree. The hardcoded
isAdult: truerepeated in all #2 examples seems like a bug waiting to happen; that should be a property dynamically computed from the age during access time, not a static thing.Or just a function. IMO computer properties are an anti pattern. Just adds complexity and confusion around what is going on - all to what? Save on a
()when you access the value?Properties make semantic sense. Functions do something, while properties are something. IMO if you want to name something lazily evaluated using a noun, it should be a property.
This is my argument against them. Computed properties do something, they compute a value. This may or may not be cheap and adds surprising behavior to the property. IMO properties should just be cheap accessors to values. If it needs to be computed then seeing a function call can hint the caller may want to cache the value in a variable if they need to use it multiple times. With properties you need to look it up to know it is actually doing work instead of just giving you a value. That is surprising behavior which IMO I dislike in programs.
that we agree on: properties should be cheap to compute.
Making a simple ternary condition as a function instead of property is a wasted opportunity to make its usage cleaner.
Make its usage cleaner? I don't see how a property does that at all. We are talking about
x.foovsx.foo()really. And IMO the latter tells you this is a function that needs to do some work even if that work is very cheap.x.fooimplies that you might be able to set the value as well. But with computed properties maybe not. Which IMO makes the program a bit harder to read and understand as you cannot simply assume it is a simple assignment or field access. It could be a full function call that does different things depending on other values or even if you are setting vs getting the value. I prefer things being more explicit.Because you're assuming
foowon't be renamed when it becomes a function. A function should start with a verb, sayget_foo(), because justfoo()tells me nothing about what the function does (or what to expect as output). If you make it a property,get_is implicit.So if the age is computed from the year of birth for example, it's really e.g.
thing.ageorthing.get_age()- both of which are fine, but I'd pick the property version.Or just
thing.age()which is fine and is fairly obvious it will return the age of the thing. And that is what is done in most languages that dont have computed properties.get_on a method really adds no value nor clarity to things. The only reasonfoo()is ambiguous is because it is a bad name - really just a place holder. Missing out the brackets here adds no value either, just makes it hard to tell that you are calling a function instead of just accessing a property.Properties are great when you can cache the computation which may be updated a little slower than every time it’s accessed. Getter that checks if an update is needed and maybe even updates the cached value then returns it. Very handy for lazy loading.
Functions can do all this. Computed properties are just syntactic sugar for methods. That is it. IMO it makes it more confusing for the caller. Accessing a property should be cheap - but with computed properties you don't know it will be. Especially with caching as your example. The first access can be surprisingly slow with the next being much faster. I prefer things to not do surprising things when using them.
I get that, it’s a valid point. But in OOP, objects can be things and do things. That’s kinda the whole point. We’re approaching detailed criticism of contextless development concepts though so it kinda doesn’t matter.