I have a couple of questions about hashes. The first is fairly simple: is there a way to set a default so that when the value for a key is changed, the object it points to is default.dup instead of default? So that if I do something like this:
lists = Hash.new([])
lists[:a].push 1
lists[:b].push 2
# Then doing the following
p lists[:a]
# Gets me
=> [1]
# Instead of
=> [1, 2]
And 'lists' is '{:a => [1], :b => [2]}' instead of '{}' with a default of '[1, 2]'.
I know why it happens this way, but is it possible to get it to behave differently? So that instead of
lists[key] = [] if lists[key].nil? # Assuming default is nil
lists[key].push value
or
lists[key] = lists[key].dup.push value # default is []
I can write simply
lists[key].push value # default is []
The second question is about setting defaults from one hash based on another. This question is more along the lines of 'Does this code violate Ruby sensibilities?'
class Hash
def add_defaults(default_hash)
raise TypeError unless default_hash.kind_of? Hash
default_hash.each { |k,v|
self[k] = v unless self.has_key? k
}
self
end
end
def some_function(str, options=Hash.new(nil))
# Set the defaults
defaults = {
:preserve_breaks => true,
:indent => 0,
:columns => 79,
}
options.add_defaults defaults
end
I have a couple of questions about hashes. The first is fairly simple:
is there a way to set a default so that when the value for a key is
changed, the object it points to is default.dup instead of default?
list = Hash.new{}
The second question is about setting defaults from one hash based on
another. This question is more along the lines of 'Does this code
violate Ruby sensibilities?'
Con fecha 2/4/2005, "Pete Elmore" <pete@petta-tech.com> escribió:
I have a couple of questions about hashes. The first is fairly simple:
is there a way to set a default so that when the value for a key is
changed, the object it points to is default.dup instead of default? So
that if I do something like this:
lists = Hash.new()
lists[:a].push 1
lists[:b].push 2
# Then doing the following
p lists[:a]
# Gets me
=> [1]
# Instead of
=> [1, 2]
And 'lists' is '{:a => [1], :b => [2]}' instead of '{}' with a default
of '[1, 2]'.
I know why it happens this way, but is it possible to get it to behave
differently? So that instead of
lists[key] = if lists[key].nil? # Assuming default is nil
lists[key].push value
or
lists[key] = lists[key].dup.push value # default is
I can write simply
lists[key].push value # default is
The second question is about setting defaults from one hash based on
another. This question is more along the lines of 'Does this code
violate Ruby sensibilities?'
class Hash
def add_defaults(default_hash)
raise TypeError unless default_hash.kind_of? Hash
default_hash.each { |k,v|
self[k] = v unless self.has_key? k
}
self
end
end
def some_function(str, options=Hash.new(nil))
# Set the defaults
defaults = {
:preserve_breaks => true,
:indent => 0,
:columns => 79,
}
options.add_defaults defaults
end
Looks like matz already provided you with a good answer,
but here's a different take since I am not sure if you
are indeed referring to default values as the language
defines them or 'just' default values for your application
logic:
"Pete Elmore" <pete@petta-tech.com> schrieb im Newsbeitrag news:424DCDEA.5020603@petta-tech.com...
I have a couple of questions about hashes. The first is fairly simple: is there a way to set a default so that when the value for a key is changed, the object it points to is default.dup instead of default? So that if I do something like this:
lists = Hash.new()
You want this:
lists = Hash.new {|h,k| h[k]=}
lists[:a].push 1
lists[:b].push 2
# Then doing the following
p lists[:a]
# Gets me
=> [1]
# Instead of
=> [1, 2]
And 'lists' is '{:a => [1], :b => [2]}' instead of '{}' with a default of '[1, 2]'.
I know why it happens this way, but is it possible to get it to behave differently? So that instead of
lists[key] = if lists[key].nil? # Assuming default is nil
lists[key].push value
or
lists[key] = lists[key].dup.push value # default is
I can write simply
lists[key].push value # default is
The second question is about setting defaults from one hash based on another. This question is more along the lines of 'Does this code violate Ruby sensibilities?'
class Hash
def add_defaults(default_hash)
raise TypeError unless default_hash.kind_of? Hash
default_hash.each { |k,v|
self[k] = v unless self.has_key? k
}
self
end
def some_function(str, options=Hash.new(nil))
# Set the defaults
defaults = {
:preserve_breaks => true,
:indent => 0,
:columns => 79,
}
