Is there a shortcut for writing all this?
def +(otherField)
@value + otherField.value
end
def -(otherField)
@value - otherField.value
end
def *(otherField)
@value * otherField.value
end
def /(otherField)
@value / otherField.value
endI was also wondering if there is a way to implement +=
total = Amount.aud(300)
total += Amount.aud(500)
total → AUD 800
?
cheers
dim
Philip Mak wrote:
Is there a shortcut for writing all this?
def +(otherField) @value + otherField.value end def -(otherField) @value - otherField.value end def *(otherField) @value * otherField.value end def /(otherField) @value / otherField.value end
Remembering that code within a class definitionbut outside a method
definition gets executed once only, when Ruby reads the class definition
in:
class Test
attr_accessor :value
def initialize(value)
@value = value
end
%w(+ - * /).each {|op|
class_eval %Q{
def #{op}(otherField)
@value #{op} otherField.value
end
}
}
end
a = Test.new(5)
b = Test.new(6)
puts a + b
Philip Mak pmak@aaanime.net wrote:
Is there a shortcut for writing all this?
def +(otherField) @value + otherField.value end
I was also wondering if there is a way to implement +=
total = Amount.aud(300)
total += Amount.aud(500)total → AUD 800
If you reimplement “+”, “+=” is reimplemented as well:
class Fixnum
def +(other)
return 5
end
end
=> nil
1 + 1
=> 5
var = 1
=> 1
var += 1
=> 5
Cheers,
Dmitri Colebatch wrote:
I was also wondering if there is a way to implement +=
total = Amount.aud(300)
total += Amount.aud(500)total → AUD 800
No need, since “x += y” is just syntax for “x = x + y”. Once you define
#+, youve got “+=” as well.
But this may not be what you want, if your #+ method returns a new
instance, and you would rather increment the object that total refers to.
In that case, you may want an #increment method and use it like:
total.increment Amount.aud(500)
Or you could define #<< to do the same thing:
total << Amount.aud(500)
The key point is that these two methods operate destructively on the
object referred to by the local variable total, whereas += assigns a new
object to that variable.
Thanks Joel et al for all the responses…
I will use IRB more
I will use IRB more
I will use IRB more
cheers
dim
Joel VanderWerf wrote:
Dmitri Colebatch wrote:
I was also wondering if there is a way to implement +=
total = Amount.aud(300)
total += Amount.aud(500)total → AUD 800
No need, since “x += y” is just syntax for “x = x + y”. Once you define
#+, youve got “+=” as well.But this may not be what you want, if your #+ method returns a new
instance, and you would rather increment the object that total refers to.In that case, you may want an #increment method and use it like:
total.increment Amount.aud(500)
Or you could define #<< to do the same thing:
total << Amount.aud(500)
The key point is that these two methods operate destructively on the
object referred to by the local variable total, whereas += assigns a new
object to that variable.