On Tuesday, 12 January 2021 at 21:37:11 UTC, Jack wrote:
I was looking for a way to avoid null checks everywhere. I was
checking the Null object pattern, or use something like enforce
pattern, or even if I could make a new operator and implement
something like C#'s .? operator, that Java was going to have
one but they refused[1] (doesn't behave exactly as C#'s
actually), Kotlin also got something in this area[2]
What some D ways to avoid those checks?
[1]:
https://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000047.html
[2]:
https://kotlinlang.org/docs/reference/null-safety.html#safe-calls
Personally, I really like functional orientation (MayBe, None,
Some... and pattern matching) avoiding the use of null, but D is
a "system" language compatible with C and null is mandatory.
Some months ago I wrote an utility template to simulate the ?.
mechanism.
The resulting syntax:
class Person
{
string name;
Person father;
this(string name, Person father){
this.name=name;
this.father=father;
}
}
Person p = new Person("Peter", new Person("John", null));
assert( p.d!"father".d!"father".d!"name".get is null);
assert( p.d!"father".d!"name".get == "John");
assert( p.d!"father".d!"name".d!"length".get(0) == 4);
assert( p.d!"father".d!"father".d!"name".d!"length".get(0) == 0);
assert( (cast(Person) null).d!"father".d!"father".d!"father".get
is null);
That is a "compact" version of a first solution using lambdas
assert(
dot(p).dot(a=>a.father).dot(a=>a.father).dot(a=>a.name).dot(a=>a.length).get(0) == 0);
Find more details here:
https://run.dlang.io/gist/392c06e745d1a35df71084ce4d29fed7
