Is it possible in Puppet to change hashes keys without calling a custom functions within a class or custom type?
Pretty much calling regular ruby functions.
$myHash.keys.each { |k| $myHash[k + "_toto"] = $myHash[k]; $myHash.delete(k) }
Related
With Puppet, in a custom ruby function is it possible to cache a value for a single catalog run?
I have this function:
Puppet::Functions.create_function(:myFunction) do
def myFunction( *arguments )
data = call_function( 'lookup', [ 'myHieraKey', nil, nil, {} ] )
data.length()
end
end
The function is called multiple times and would be more optimal if each invocation didn't query hiera.
I can't seem to find any hints as to how to do this. A quick and dirty way could be to define a unique class variable, however this pollutes one of the Puppet classes.
##mymodule_myfunction_myvariable = {}
Is there a "proper" way?
In ruby, the following expression:
x.filter {|n| n.even?}
can also be written as:
x.filter(&:even?)
so, I am wondering how I would write this expression?
x.filter {|n| !n.even?}
without using odd? method
As Sam and engineerskmnky said in the comments below question, it is not possible to perform x.filter { |n| !n.even? } operation directly (and in fact two operations inside the block).
I guess that this was only a trivial example and not a real code so if you have method that does not have the inverse one and you don't want to create one, you can create a lambda or proc in the following way:
not_even = -> (n) { !n.even? }
and then call it on filter as:
x.filter(¬_even)
You can also use reject method which should give you the same result without the magic of using lambda.
I am looking for a function which can get me all the keys from hash or I can loop through the hash to retrieve single key at a time.
Currently I am hardcoding key
VALUE option = rb_hash_aref(options, rb_str_new2("some_key"));
You can iterate over the key/value pairs with a callback function using rb_hash_foreach (blog post w/an example):
void rb_hash_foreach(VALUE, int (*)(ANYARGS), VALUE);
There is an rb_hash_keys in MRI, but it's not in any header files it seems, so using it may be risky.
You could always make a call to the Ruby method itself:
VALUE keys = rb_funcall(hash, rb_intern("keys"), 0)
Does Groovy have something similar to bang methods on Ruby?
From this blog post:
In Ruby, you can write methods whose names end in ! (exclamation point or “bang”). There’s a lot of confusion surrounding the matter of when, and why, you would want to do so.
The ! in method names that end with ! means, “This method is dangerous”—or, more precisely, this method is the “dangerous” version of an otherwise equivalent method, with the same name minus the !. “Danger” is relative; the ! doesn’t mean anything at all unless the method name it’s in corresponds to a similar but bang-less method name.*
And this site:
You'll find a number of pairs of methods, one with the bang and one without. Those without the bang perform an action and return a freshly minted object, reflecting the results of the action (capitalizing a string, sorting an array, and so on). The bang versions of the same methods perform the action, but they do so in place: Instead of creating a new object, they transform the original object.
This is not a convention in Groovy like it is in Ruby. However you can write methods with names that contain characters like ! with the limitation that it must always be quoted like a string:
// define method with quoted name
def 'dangerous!'() {
// do something dangerous
}
// invoke method with quoted name
'dangerous!'()
No, groovy (currently as of v2.1.4) doesn't have anything like this
To add to your options, another solution that would be more Groovy-like or Java-like would be to include an optional parameter that enabled in-place (a.k.a. dangerous) modification, like so:
def processFoo(Foo item, mutate = false) {
if(!mutate) {
Foo temp = new Foo()
// copy item properties
item = temp
}
item.bar = 'blah blah'
// process item here
return item
}
processFoo(myFoo) // makes a copy
processFoo(myFoo, true) // modifies original
This pattern is used — albeit in the opposite manner — with the sort method on collections. Calling sort(false) on Lists prevents changing the original array. Calling sort() or sort(true) will modify it directly.
I have a method drive that goes like this:
public double drive(double milesTraveled, double gasUsed)
{
gasInTank -= gasUsed;
return totalMiles += milesTraveled;
}
I know I can't return multiple values from a method, but that's kind of what I need to do because I need both of these values in my main method, and as it is now it's obviously only returning the one. I can't think of anything that would work. Sorry if this is a super beginner question. What can I do to get both values to return from the method?
You can return multiple value from a function. To do this You can use structure.
In the structure you can keep required field and can return structure variable after operation.
You can also make a class for the required field if You are using OOPS supporting language but Structure is best way.
In most languages you can only return a single value from a method. That single value could be a complex type, such as a struct, array or object.
Some languages also allow you to define output parameters or pass in pointers or references to outside storage locations. These kinds of parameters also allow you to return additional values from your method.
not sure, but can you take array of your values?
array[0]=gasInTank;
array[0] -= gasUsed;
array[1]=milesTraveled;
array[1] -= milesTraveled;
return array;