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    User @CyrusNajmabadi unbanned @VBAndCs
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  • Jan 31 2019 21:39

    gafter on master

    Propose Feb 11 agenda (#2187) (compare)

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    gafter closed #2187
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    MarkPflug opened #2189
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    MohammadHamdyGhanem opened #2188
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    gafter review_requested #2187
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    gafter review_requested #2187
  • Jan 30 2019 20:01
    gafter review_requested #2187
Eyal Alon
@eyalalonn
@HaloFour Thanks.
masonwheeler
@masonwheeler
Anyone know why the latest version of Visual Studio has stopped showing me grayed out usings that aren't used in the file, but only for some projects and not others?
CyrusNajmabadi
@CyrusNajmabadi
File issue. Sounds like a regression.
masonwheeler
@masonwheeler
Is it possible to put an Attribute marked as [AttributeUsage(AttributeTargets.Constructor)] on the autogenerated constructor from a record?
Joe4evr
@Joe4evr
@masonwheeler doesn't look like it from a little rudimentary experimentation, see if there's an open discussion
HaloFour
@HaloFour
@masonwheeler Where does Delphi have inherited constructors?
masonwheeler
@masonwheeler

@HaloFour The entire language. If you define a constructor on a base class, you can use it on any of its descendants. The place it gets really useful, though, is when you start working with virtual constructors. You can call a virtual constructor with a metaclass reference, pass in the parameters, and get an instance of the class in question.

As I mentioned on the Github discussion, this was largely put in place to support form deserialization. The DFM (form data) files have class names in them, and the RTTI system has something functionally equivalent to a string->metaclass dictionary for all of the Component types used in your program. So you take your class name, get a metaclass from there, invoke the virtual constructor, and you have a Component-typed reference whose actual type is the class you wanted. Use RTTI to fill in the properties, then repeat recursively on all the child components until you have your whole form.

HaloFour
@HaloFour
So that's specifically related to constructors marked as virtual, otherwise it works like other OOP languages where the derived class can call the base constructor but you can't create the derived class by calling the base constructor.
masonwheeler
@masonwheeler
Nope. :point_up:
If you define a constructor on a base class, you can use it on any of its descendants.
HaloFour
@HaloFour
Even if it defines its own constructors that require additional parameters?
masonwheeler
@masonwheeler
type BaseClass = class
   constructor Create(value: integer);
end;

DerivedClass = class(BaseClass)
   constructor Create(value1: integer; value2: string);
end;

...

MyObj := DerivedClass.Create(5); //this is perfectly valid
HaloFour
@HaloFour
Wow, that feels so wrong
masonwheeler
@masonwheeler
It's not what you're used to.
And it's not particularly idiomatic.
But the language specification does not forbid it.
HaloFour
@HaloFour
Does the compiler warn about it?
Was kinda hoping Oxygene had an online playground but it doesn't seem to
masonwheeler
@masonwheeler
I don't think so. It's been a while since I've worked with Delphi, and I know some people were asking for warnings on scenarios like that, so more recent versions might, but I wouldn't bet on it.
Oh, well you definitely can't do that in Oxygene. It's a CLR language and that's forbidden by the CLR.
HaloFour
@HaloFour
Sure, but I understand that it emits stuff to smooth over the differences
Like metaclasses
masonwheeler
@masonwheeler
true
HaloFour
@HaloFour
That would drastically affect how I might design object hierarchies, I'd probably intentionally avoid inheritance in more cases, especially if the only safeguard would be to override and throw.
masonwheeler
@masonwheeler
Some of it's just philosophy. Why do you need a "safeguard"? If someone else inherits from your class and gets the constructors wrong, that's on them, not you.
HaloFour
@HaloFour
I find it very common to want to define a base class that requires additional state at construction.
The inability to force the correct call on the consumer feels very wrong to me
And without overriding and throwing a consumer could very easily accidentally create an instance in an incomplete state.
masonwheeler
@masonwheeler
🤷‍♂️ Different language, different idioms. "Could very easily," yes, but in practice it doesn't tend to happen.
HaloFour
@HaloFour
Must rely a lot less on constructors
But this is why virtually no other OOP language has such a thing.
"Construction is separate from consumption"
Anyways it is interesting to hear that there are languages that don't follow that approach. I recall Delphi being around in the mid 90s but I knew almost nobody who actually worked in it. I recall it being stupidly expensive.
I used to keep in touch with a dev who worked on the Oxygene compiler but we haven't chatted in a long time
masonwheeler
@masonwheeler
Yup. That's what drove it into the ground. Corporate refused to acknowledge that it couldn't effectively compete with free versions of .NET and Java and Python at a high-3-figures minimum-SKU price point.
HaloFour
@HaloFour
As I recall it, the minimum SKU wasn't exactly sufficient for business app development either. I recall Borland's site implying that if you needed DB connectivity that the price was several thousand.
masonwheeler
@masonwheeler
Yup. It's gotten better over the years, but... too little too late.
HaloFour
@HaloFour
I don't doubt that Delphi was the better product but it's definitely hard to compete with VB when your product is an order of magnitude more expensive
masonwheeler
@masonwheeler

It kind of depends. If you're a software company with a budget, that hardly matters.

What does matter, though, is when your software company can't hire any devs because no one knows how to use your programming language because they weren't taught it in school and didn't pick it up as a hobby because there were plenty of free alternatives available.

Antony Male
@canton7
Heh, I do consultancy stuff where we constantly have to pick up new languages/tools. The cost of training someone up on a new language has to be a small fraction of the cost of hiring someone in the first place, surely?
HaloFour
@HaloFour
I was taught Pascal in school, but no cheap business wants to pay more than they have to for tools :)
masonwheeler
@masonwheeler
Training someone on the basic syntax and semantics is easy, if they're already a competent programmer. Training someone to know and internalize the idiomatic patterns of the language and be familiar with its ecosystem? That takes years.
HaloFour
@HaloFour
@canton7 I think that's largely true, at least within languages of similar paradigms. Probably more effort to learn the differences of any given framework than the syntax of the language.
masonwheeler
@masonwheeler

no cheap business wants to pay more than they have to for tools

Which is why so many of them go out of business. Being cheap often means not understanding the difference between a cost and an investment. Remember, you make your money when you buy, not when you sell.

HaloFour
@HaloFour
Which is why the investment needs to demonstrate why it's worth the cost and how it has better ROI.
It didn't help Borland that VB programmers were substantially more common and generally less expensive as well.
Antony Male
@canton7

Training someone on the basic syntax and semantics is easy, if they're already a competent programmer. Training someone to know and internalize the idiomatic patterns of the language and be familiar with its ecosystem? That takes years.

I'm not sure years is fair. Months, sure. Years gets you the equivalent of someone who reads all the language design meeting minutes, and you don't need that to be a competent programmer. But the cost of hiring someone is measured in months' salary anyway, and you're getting some level of value before they're fully competent

masonwheeler
@masonwheeler

It didn't help Borland that VB programmers were substantially more common and generally less expensive as well.

Yeah, that's the next step from my "what does matter," above. When companies have trouble hiring devs for your language, it makes them less inclined to use your language.

And they never understood that. It's the same old story of the Blockbuster executives who, even in the face of Netflix bearing down on them like a steamroller approaching a cartoon coyote, didn't want to get rid of late fees because they were bringing in too much money.
COCPORN
@COCPORN
I am a little stumped at something I am seeing. I am implementing an interface and deriving from an abstract class which implements some of the methods in the interface. Yet VS and the compiler both seem to force me to implement the methods in the derived class. There is a 100% chance I am doing this wrong, yet I cannot really see how. Any gut reactions that would help me on my journey to create the best rock song ever?
COCPORN
@COCPORN
Figured it out. I will go find my seat at the back of the shortbus. :) Thanks for being my rubber duck.