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    Matthew J. Clemente
    @mjclemente
    I think this is the appropriate forum for this question.
    I’m trying to establish guidelines for when to manually throw errors within my app.
    For example, I have a function within a bean that should only run when it's a "draft". I could include logic within the function to account for this (check if draft, if not, create and return it), or, I could throw an error with a message about the restriction.
    Sean Corfield
    @seancorfield
    The guiding question around exceptions is: is this an expected condition that I should be able to handle?
    If calling that function without a draft is "expected" and the function could reasonably auto-create and return the new draft, then do that.
    Matthew J. Clemente
    @mjclemente
    I guess, in this case, I’m trying to guide the application. I could account for whether it is a draft, but I think the application will run better if I don’t need to account for that.
    So I’m making a business rule that it needs to be.
    Sean Corfield
    @seancorfield
    An exception says: "Nope, sorry, I don’t know how to deal with this request" (as opposed to "Nope, I know about that but it’s an error").
    Matthew J. Clemente
    @mjclemente
    Is there a preferred way to handle the latter?
    Sean Corfield
    @seancorfield
    Depends on the language context and what the function does / is expected to return.
    For example, functions that "do something" (and return nothing), can return a success / failure indicator instead.
    Functions that return something specific on success, can return nothing on failure (null in Java, for example), or perhaps a struct with a success / failure indicator and a result key when success and a codes key when failure.
    It really depends on what you’re trying to do. There’s no one size fits all here.
    I have my validation functions return arrays of error descriptions, for example. So they return an empty array for success / no errors.
    Lookup functions generally return a "thing" (success) or null (failure).
    I’ll use a boolean result if all I care about is generically "Yes, I did it!" or "Nope, sorry, no can do!".
    Matthew J. Clemente
    @mjclemente
    In this case, in broad strokes, an value is being saved, and then assigned to a “page”. So the value gets validated/saved. Then I pass it into the page bean, which has a function to save the value to a linking table for the page.
    Sean Corfield
    @seancorfield
    (but, again, throwing an exception for "Halp! I haz no cluez!" is still reasonable)
    Matthew J. Clemente
    @mjclemente
    So, right now it returns void… but that’s mostly becuase it’s just doing an insert that I’m assuming is successful.
    The issue is that the page it is being saved to needs to be a “draft”. The page knows whether it is a draft or not.
    But I’d rather insist that my controller (or other calling functions) always make sure they have a draft page called, before they try to save the value.
    (hope I’m explaining this clearly)
    Sean Corfield
    @seancorfield
    Sounds like you’d prefer an exception then, rather than silent auto-creation of the draft.
    Matthew J. Clemente
    @mjclemente
    yeah, only because the silent auto-creation can be expensive
    If there are a number of values that need to be saved (which there can be in some cases)
    Is that lazy? Falling back on the exception?
    Sean Corfield
    @seancorfield
    No, that fits the rule perfectly: you should always create any necessary drafts before calling this function (else it will throw an exception).
    Matthew J. Clemente
    @mjclemente
    Thanks. I guess, returning full circle, it fits with the guideline you provided (is this an expected condition that I should be able to handle?)
    Sean Corfield
    @seancorfield
    Yup. And you’re deciding, from a business p.o.v., that "no, this function should not handle that task".
    Matthew J. Clemente
    @mjclemente
    If the rule (drafts only) makes the condition unexpected, it’s acceptable to throw the exception