Questions tagged [safe-navigation-operator]
28 questions
272
votes
22 answers
Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?
I'll explain by example:
Elvis Operator (?: )
The "Elvis operator" is a shortening
of Java's ternary operator. One
instance of where this is handy is for
returning a 'sensible default' value
if an expression resolves to false or
null. A…
tiagomac
- 2,935
- 2
- 15
- 6
27
votes
3 answers
Safe navigation operator (&.) for nil
As Ruby 2.3 introduces the Safe navigation operator(&.), a.k.a lonely operator, the behavior on nil object seems odd.
nil.nil? # => true
nil&.nil? # => nil
Is that designed to behave like this way? Or some edge case that slipped away when…
sbs
- 4,102
- 5
- 40
- 54
26
votes
7 answers
Safely assign value to nested hash using Hash#dig or Lonely operator(&.)
h = {
data: {
user: {
value: "John Doe"
}
}
}
To assign value to the nested hash, we can use
h[:data][:user][:value] = "Bob"
However if any part in the middle is missing, it will cause error.
Something like
h.dig(:data, :user,…
sbs
- 4,102
- 5
- 40
- 54
25
votes
4 answers
Is there something like a Safe Navigation Operator that can be used on Arrays?
I have used Safe Navigation Operator for Objects to load on Asynchronous calls and it is pretty amazing. I thought I could reproduce the same for Arrays but it displays a template parse error in my Angular code. I know *ngIf is an alternative…
Sriram Jayaraman
- 800
- 1
- 8
- 15
21
votes
1 answer
Why does Ruby use its own syntax for safe navigation operator?
Ruby 2.3.0 introduces the safe navigation syntax that eases the nil handling of chained method calls by introducing a new operator that only calls the method if value of previous statement is not nil. This is a feature that already exists for…
Roope Hakulinen
- 7,326
- 4
- 43
- 66
5
votes
4 answers
Does Ruby safe navigation operator evaluate its parameters when its receiver is nil?
Question:
Does Ruby safe navigation operator (&.) evaluate its parameters when its receiver is nil?
For example:
logger&.log("Something important happened...")
Is the "Something important happened..." string evaluated here?
Could you provide an…
Marian13
- 7,740
- 2
- 47
- 51
4
votes
2 answers
Access Observable in the Template without using the Safe Navigation Operator and Async Pipe Everytime
I'm new to angular and struggle a little with rxjs and all the async stuff going on.
Some Context
Lets assume you have a website like facebook with profiles. You can reach a profile by navigating to website.com/profiles/profileUrl. Equally when…
Younes El Ouarti
- 2,200
- 2
- 20
- 31
4
votes
2 answers
Why does the null-conditional operator change regular property access?
I'm confused about how the null-conditional operator cascades with normal property access. Take these two examples:
a?.b.c
(a?.b).c
I would expect them to be equivalent: first, the value of a?.b is evaluated, then result.c is evaluated. Thus if a…
BlueRaja - Danny Pflughoeft
- 84,206
- 33
- 197
- 283
4
votes
2 answers
NilCheck fix on safe navigation operator (&.)
This simple method on a class just run the status method using the safe navigation operator.
def current_status
account&.status
end
But reek report this warning:
MyClass#current_status performs a nil-check…
AndreDurao
- 5,600
- 7
- 41
- 61
3
votes
1 answer
Safe navigation operator for hash with string keys
I have a problem:
data = { 'str_key' => ['string1', 'string2'] }
# @param [Hash] data - hash with String key
# @return [boolean]
def some_logic_test?(data)
data&..include?('string1')
end
How can I use the safe…
Radosław Sakowicz
- 101
- 2
- 8
3
votes
2 answers
Ruby: Safe-navigation operator, undefined method `call`
I am trying to compare a number literal with the return value of a function that could return nil or a numeric. Consider this:
def unreliable
[nil, 42].sample
end
unreliable > 10
This will blow up 50% of the time with NoMethodError: undefined…
Ethan Kent
- 381
- 1
- 4
- 20
3
votes
2 answers
What is the pre-Ruby2.3 equivalent to the safe navigation operator (&. or "ampersand-dot")?
The answers to every question I can find (Q1, Q2) regarding Ruby's new safe navigation operator (&.) wrongly declare that obj&.foo is equivalent to obj && obj.foo.
It's easy to demonstrate that this equivalence is incorrect:
obj = false
obj &&…
user513951
- 12,445
- 7
- 65
- 82
1
vote
0 answers
Returning result of statement including the safe navigation operator as boolean
I just started using the safe navigation operator in C# for the first time and I am wondering wether this is a correct use case for that operator:
public bool HasAttributes
{
get
{
return this.SomeClassMember?.Attributes?.Count > 0;
…
Chris
- 1,417
- 4
- 21
- 53
1
vote
1 answer
Where should I use Safe Navigation (Elvis Operator, the "?") in Angular?
We undoubtedly use safe navigation in string interpolation ({{}}) to safely navigate values in a nested object with checking nulls or undefined.
I have a question that, is it okay to use safe navigation also for:
ngIf
ngFor
ngModel
ngClass
and…
Faizan Saiyed
- 804
- 3
- 17
- 33
1
vote
0 answers
Is safe navigation operator have drawbacks on performance in Angular 2+
It's known that first ngOnChanges fires before bindings are initialized.
So it's common to add safe navigation operator into expressions.
@Component({
changeDetection: ChangeDetectionStrategy.OnPush,
selector: 'some-component',
…
Dzmitry Vasilevsky
- 1,295
- 2
- 14
- 25