I have tho classes A and B1, and b is defined as:
a = A.new
b = a.foo # b is an instance of class B1
I would like to define b directly:
b = B2.new
where the class B2 is defined:
class B2
def initialize
a = A.new
self = a.foo # <<< error!
end
...
end
But i cannot define self in the constructor...
How can i solve this problem.
Thanks on advance,
iwan
--
Posted via http://www.ruby-forum.com/.
You cannot re-define self, it is defined for you to be the current instance of class B2. Why do you need it? Even if it were possible, don't you find it weird - you create and instance of B2 with B2.new, but get back the instance of B1?
Gennady.
On Aug 8, 2012, at 3:32 AM, Iwan B. wrote:
I have tho classes A and B1, and b is defined as:
a = A.new
b = a.foo # b is an instance of class B1I would like to define b directly:
b = B2.newwhere the class B2 is defined:
class B2
def initialize
a = A.new
self = a.foo # <<< error!
end
...
endBut i cannot define self in the constructor...
Hi,
This makes no sense. Even if you could redefine "self", it's certainly a
bad idea to change the way objects are created.
So you'll have to stick with the class method (though I have no idea
what this is for).
--
Posted via http://www.ruby-forum.com/.
This is the 'real' case (used for .xlsx files generation, via axlsx
gem):
p = Axlsx::Package.new
wb = p.workbook
wb.styles.add_style sz: 16, b: true, alignment: { horizontal: :center }
wb.add_worksheet(:name => "Basic Worksheet") do |sheet|
...
I don't need the package object 'p', except for get a workbook. But i
want to create a custom worksheet class, so i can define my predefined
styles:
Inside initialise method:
@my_styles = {}
@my_styles[:heading] = styles.add_style sz: 16, b: true, alignment: {
horizontal: :center }
def apply_style(name)
@my_styles[name.to_sym]
end
Remark that 'styles' is a workbook method.
Finally:
wb = MyWorkbook.new
...
sheet["B1"].style = wb.apply_style :boo
Thank you!
--
Posted via http://www.ruby-forum.com/.
Iwan B. wrote in post #1071643:
class B2
def initialize
a = A.new
self = a.foo # <<< error!
end
...
end
It *is* possible to override the 'new' method:
class B2
def self.new
return A.new
end
end
But this is very likely to confuse people who call B2.new and expect to
get an instance of B2.
If you want to choose the class dynamically then the normal approach is
a factory method:
class B2
def self.create(*args)
klass = pick_a_class # choose your own logic here
klass.new(*args)
end
end
But it seems to me that subclassing is closest to what you're trying to
achieve (making something which is like a workbook, but slightly
modified)
--
Posted via http://www.ruby-forum.com/\.
And especially instance "a" would be lost unless instances of class B1
have a reference back to an instance of A. Basically instance of A in
this scenario is completely superfluous. If B1's can only be created
via A.new then a method like this would be the way to go
def create(...)
A.new(...).foo
end
Kind regards
On Wed, Aug 8, 2012 at 12:54 PM, Jan E. <lists@ruby-forum.com> wrote:
This makes no sense. Even if you could redefine "self", it's certainly a
bad idea to change the way objects are created.
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
This is the 'real' case (used for .xlsx files generation, via axlsx
gem):
p = Axlsx::Package.new
wb = p.workbook
Well, you could do
class MyPackage < ::Axlsx::Package
class MyWorkbook < ::Axlsx::Workbook
def initialize(*a, &b)
super
# add styles
end
end
def workbook
MyWorkbook.new(self)
end
end
Or, if you just want to add default styles and values you could do
def ::Axlsx::Workbook.my_workbook
workbook.tap do |wb|
wb.styles.add_style sz: 16, b: true, alignment: { horizontal: :center }
...
end
end
wb.styles.add_style sz: 16, b: true, alignment: { horizontal: :center }
wb.add_worksheet(:name => "Basic Worksheet") do |sheet|
...I don't need the package object 'p', except for get a workbook.
It _may_ be stored inside the workbook.
Cheers
robert
On Wed, Aug 8, 2012 at 2:05 PM, Iwan B. <lists@ruby-forum.com> wrote:
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/