How to call a function of the base class?

Toit

#How to call a function of the base class?

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kaxori 06/13/2025 04:46 PM

If a derived class and its base class have both the same function implemented. But if the base calls its function the function of the derived class is executed. How can I force to call the base class function ?

floitsch 06/13/2025 04:47 PM

You can call super.
example:

class A:
  foo x:
    print "from A: $x"

class B extends A:
  foo x:
    super (x + 1)

kaxori 06/13/2025 05:05 PM

class Base:
  f m/string: print "Base: $m"
  b:   f "b"

class Derived extends Base:
  f m/string: print "Derived: $m"
  d: b

main:
  c := Derived
  c.d

What I expected is that b calls Base, but what is get is "Derived"

kaxori 06/13/2025 05:05 PM

class A can't know that it is derived.

floitsch 06/13/2025 05:05 PM

every call in Toit is virtual, except for direct super calls.

floitsch 06/13/2025 05:06 PM

Extending classes is one of the most tight ways of binding two different classes. It should be done with care.

floitsch 06/13/2025 05:07 PM

this is just one example, but there are many others, where changing the base or derived class can lead to unexpected behavior.

kaxori 06/13/2025 05:07 PM

Aha: i use the function to log things. And now wondered that always the derived log-ID appears.

floitsch 06/13/2025 05:07 PM

kaxori 06/13/2025 05:09 PM

every call in Toit is virtual

that is new for me and now the behaviour makes sense.
Thank you

kaxori 06/13/2025 05:11 PM

I need to read a language concept doc ...

bitphlipphar 06/14/2025 06:21 AM

You could make the f functions static?(edited)

bitphlipphar 06/14/2025 06:24 AM

class Base:
  static f m/string: print "Base: $m"
  b: f "b"

class Derived extends Base:
  static f m/string: print "Derived: $m"
  d: b

main:
  c := Derived
  c.d

floitsch

every call in Toit is virtual, except for direct super calls.

bitphlipphar 06/14/2025 06:25 AM

... and except for calls to top-level or static functions.

bitphlipphar 06/14/2025 06:26 AM

The downside to making these static is that you have to pass the instance (this) to f if you want to access the instance from within f.

kaxori 06/14/2025 09:51 AM

Thank you.
Where can I find the holy toit bible

floitsch 06/14/2025 09:52 AM

Some of it is here: https://docs.toit.io/language
Probably still some things missing.
The object model is also relatively similar to Java's and/or Dart's.(edited)

kaxori 06/14/2025 09:57 AM

I drink coffee and I play darts

grew up reading books (Kernighan, Ritchy, Stroustrup)

floitsch 06/14/2025 09:57 AM

Java, C#, Dart, and Toit all have pretty similar (core) object models.

floitsch 06/14/2025 09:59 AM

With time, they add more features (extension methods, ...), but at their core they still are the same: classes with interfaces, and all method calls are virtual.

kaxori 06/14/2025 10:01 AM

...and the way (making you happy) to program µC's is Toit!

21 messages in total