Function appends same value to string based on number of function calls

Ruby
1

Hi Guys,

Is this default ruby behaviour or is this a bug? Based on the number
of call to Testappend::get_some_value, the string “-New Value” is
appended x number of times. If you first assign value = ‘’ instead of
value = @text, the behaviour is different and the “-New Value” string
is appended only once.

version of ruby: ruby 1.8.6 (2007-03-13 patchlevel 0) [x86_64-linux]

Thanks.

Philippe

module ATest

def ATest.main

t = TestAppend.new
puts t.get_some_value ==> Start of string-New Value
puts t.get_some_value ==> Start of string-New Value-New Value
puts t.get_some_value ==> Start of string-New Value-New Value-New

Value

end

class TestAppend
attr_accessor :text

def initialize(attributes = {})
  @text = "Start of string"
end

def get_some_value
  value = @text
  value << '-New Value'
  return value
end

end

end

ATest::main

2

On Apr 24, 2008, at 2:00 PM, [email protected] wrote:

Hi Guys,

Is this default ruby behaviour or is this a bug? Based on the number
of call to Testappend::get_some_value, the string “-New Value” is
appended x number of times. If you first assign value = ‘’ instead of
value = @text, the behaviour is different and the “-New Value” string
is appended only once.

Do you mean:
def get_some_value
value = ‘’
value << ‘-New Value’
return value
end

If so, where do you do anything with the String object to which @text
refers?

BTW, you could simplify your original to just:
def get_some_value
@text << ‘-New Value’
end

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

3

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 value << '-New Value'
 return value

end

end

value = @text does not copy the string and << doesn’t return a string
but modifies the receiver in place.

What you are doing is getting a reference to @text which just has
another name. Then you modify @text by using << on value (which is the
same object as @text).

If you do not wish to modify @text, use “+” or string interpolation.

===code===
def get_some_value
@text + “-New Value” #dies if @text == nil
end
#or
def get_some_value
“#{@text}-New Value” #doesn’t die, but looks ugly if @text == nil
end
===code===

Regards,
Florian G.
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4

On Apr 24, 11:11 am, Rob B. [email protected]
wrote:

Do you mean:
def get_some_value

Thanks.
puts t.get_some_value ==> Start of string-New Value
@text = “Start of string”
end

ATest::main

Rob,

I do not want to assign a new value to @text.
The “get_some_value” function should return a new string (value) which
is a concatenation of strings. In this case a simple concatenation of
@text and “-New Value”.

#This version will work and does not append “-New Value” x times based
on the number of function calls.
def get_some_value
value = ‘’
value = @text
value << ‘-New Value’
return value
end

Thank you for your help,

Philippe

5

On Apr 24, 11:35 am, [email protected] wrote:

of call to Testappend::get_some_value, the string “-New Value” is

Rob B. http://agileconsultingllc.com

module ATest

 return value

I do not want to assign a new value to @text.
return value
end

Thank you for your help,

Philippe

Sorry, this works, the second line is << instead of =

def get_some_value
value = ‘’
value << @text
value << ‘-New Value’
return value
end

Philippe

6

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[email protected] wrote:
| Rob,
|
| I do not want to assign a new value to @text.
| The “get_some_value” function should return a new string (value) which
| is a concatenation of strings. In this case a simple concatenation of
| @text and “-New Value”.

def return_some_value
~ “#{@text} -New Value”
end

new_string = MyClass.return_some_value

Phillip G.
Twitter: twitter.com/cynicalryan

~ - You know you’ve been hacking too long when…
…your digital alarm clock goes off and you think “Bloody Macs!”
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7

On Apr 24, 11:47 am, Florian G. [email protected] wrote:

end
but modifies the receiver in place.
end

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Thank you for the explanation.

Philippe

8

On Apr 24, 11:47 am, Florian G. [email protected] wrote:

end
but modifies the receiver in place.
end

iEYEARECAAYFAkgQ1dcACgkQJA/zY0IIRZa6kQCeLJ8P6Dz1Gj9WBUWM73n0LGcU
0McAnjzeEwBTNtYBkJatMDKMORNcdO/f
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Thank you for the explanation.

Philippe

9 
def get_some_value
  value = @text
  value << '-New Value'
  return value
end

You are appending to the string object pointed to by “value”, which is
the same object “@text” is pointing to.

You might want:

def get_some_value
“#{@text}-New Value”
end

mfg, simon … hth