Introduction to Dart for Beginners - Generics, Factories, Enums and Exceptions - Part Seven

In this video we look at Generic Types, Factory Constructors, Enumerated Types, Exceptions, and Singletons.

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[fooked]

Packed with so much info! A little unclear about those cascade operators.

Thanks for another great one!

[minutesseries]

Thanks man, came here to understand factory

[talentoutput]

Thanks..Tensor. Your tutorials are awesome.

[techytimo]

I didnt get the constructor notation on the subclasses:
Cat(String type) : super._type(type);
Is that a short form and how does the long for look? or what does this statement mean?

[bertlashes]

6:40 if stopped has index 0, and running has index 1, wouldn't paused have index 2, as opposed to 3?

[dexterstm]

9:40 Did u mean it would have an index of 2 instead of 3?

[Dorumin]

19:40 no need to cascade in the if statement, you're already reassigning it in the return expression :P

[jasonnelford]

Great video! One question: why does the toString() method inside the Person class automatically force the print(pub.drinking) expression in the main() function to print the list showing the names of the people, rather than the [Instance of 'Person', Instance of 'Person']? We never actually call this toString() method anywhere, so why does this automatically happen?

[varunhegde]

I have one elementary question, I know by declaring variable static, memory will be allocated separately in the beginning. So how will compiler get to know how much memory to allocate to a item variable when Class itself not defined yet.
Thanks in advance.

[kirill]

Thank you! Perfectly picked examples for understanding the topic.

The only question I have is: do we actually need to use factory for a singleton?

Why couldn't we just create a private default constructor and a static getInstance() method like in good old Java?

[WorstDeveloper]

Can't you say:
if (status == Status.running)
instead of:
if (status.index == 1)

I think the first one is clearer, and would protect against possible bugs if reordering items in the enum.

[WorstDeveloper]

I know it's just an example, but I don't think the checkAge function should throw an exception if the person is underage.
instead it should probably just return true/false.