I find your example of Typeguard a little problematic precisely because it is subject to fail in the case of "interface growth". Determining type based on the presence of a method looks really flaky to me. As already suggested a duck would be identified as a fish. In your example code it makes much more sense to simply check for the presence of the swim method (i.e. canSwim()); rather than checking against the type*.
I appreciate it's sometimes hard to find simple real-world examples; but in this case you either need to find a better one or add a health warning: your isFish method is very likely to introduce hard to trace bugs in future and defeats the very purpose of using TS.
Apart from that I found the article useful ;)
* In the same way you should prefer 'feature detection' over 'browser detection'.
Hello ! As I said in another comment the aim of this example is to understand what is a Typeguard ! My example doesn't reflect the reality since as you said, Duck can be identificated as Fish !
In a real project you should use another way to make the difference between each class :)
In a real project you should use another way to make the difference between each class
Indeed; that was precisely my point: it's an ill-conceived example and demonstrates how not to use Typescript. There's little point demonstrating that functionality exists if you don't also demonstrate the thought processes required to use it properly.
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I find your example of Typeguard a little problematic precisely because it is subject to fail in the case of "interface growth". Determining type based on the presence of a method looks really flaky to me. As already suggested a duck would be identified as a fish. In your example code it makes much more sense to simply check for the presence of the swim method (i.e.
canSwim()); rather than checking against the type*.I appreciate it's sometimes hard to find simple real-world examples; but in this case you either need to find a better one or add a health warning: your
isFishmethod is very likely to introduce hard to trace bugs in future and defeats the very purpose of using TS.Apart from that I found the article useful ;)
* In the same way you should prefer 'feature detection' over 'browser detection'.
Hello ! As I said in another comment the aim of this example is to understand what is a Typeguard ! My example doesn't reflect the reality since as you said, Duck can be identificated as Fish !
In a real project you should use another way to make the difference between each class :)
Thank you for your comment a lot !
Indeed; that was precisely my point: it's an ill-conceived example and demonstrates how not to use Typescript. There's little point demonstrating that functionality exists if you don't also demonstrate the thought processes required to use it properly.