Calling methods, getting string and adding them

Ruby
1

I was wondering why this is not being accepted? I get an error stating
that + is an unknown method.

I defined a Class and 3 methods within the class, and am merely calling
the methods and trying to add them together for display from one line:

m.ClassMethodString + " " + m.ClassMethodString + ": " +
m.ClassMethodInteger.to_s

2

On 14/06/12 08:48, Michael S. wrote:

I was wondering why this is not being accepted? I get an error stating
that + is an unknown method.

I defined a Class and 3 methods within the class, and am merely calling
the methods and trying to add them together for display from one line:

m.ClassMethodString + " " + m.ClassMethodString + ": " +
m.ClassMethodInteger.to_s

Please post your class, or even better the entire code =]

Sam

3

On Thu, 2012-06-14 at 05:54 +0900, Sam D. wrote:

Please post your class, or even better the entire code =]

And the actual error… most likely your function isn’t returning a
string. The error should tell you want class ‘+’ is not defined in. For
example, if your method returns nil you’ll get:

NoMethodError: undefined method `+’ for nil:NilClass

Easiest fix would be to call to_s on the return value of your methods
(e.g. m.ClassMethodString.to_s) but that might merely cover-up some
problem with your method’s return value.

-Paul

4

On Thu, 2012-06-14 at 09:05 +0900, Ryan D. wrote:

On Jun 13, 2012, at 14:26 , Paul Sutton wrote:

Easiest fix would be to call to_s on the return value of your methods
(e.g. m.ClassMethodString.to_s) but that might merely cover-up some
problem with your method’s return value.

No. The easiest fix is to use string interpolation.

Easiest is subjective - but yes, I think string interpolation is in
general a better solution when outputting a string.

5

On Jun 13, 2012, at 21:24 , Paul Sutton wrote:

Easiest is subjective - but yes, I think string interpolation is in
general a better solution when outputting a string.

It is measurable by the number of methods called and the number of
garbage objects created.

6

On Jun 13, 2012, at 14:26 , Paul Sutton wrote:

Easiest fix would be to call to_s on the return value of your methods
(e.g. m.ClassMethodString.to_s) but that might merely cover-up some
problem with your method’s return value.

No. The easiest fix is to use string interpolation.

7

On Thu, 2012-06-14 at 13:32 +0900, Ryan D. wrote:

On Jun 13, 2012, at 21:28 , Ryan D. wrote:

On Jun 13, 2012, at 21:24 , Paul Sutton wrote:

Easiest is subjective - but yes, I think string interpolation is in
general a better solution when outputting a string.

It is measurable by the number of methods called and the number of garbage
objects created.
…
2111 % ruby -rtracer -e ‘“a#{1}b#{2}c”’
#0:-e:1::-: “a#{1}b#{2}c”
#0:-e:1:Fixnum:>: “a#{1}b#{2}c”
#0:-e:1:Fixnum:<: “a#{1}b#{2}c”
#0:-e:1:Fixnum:>: “a#{1}b#{2}c”
#0:-e:1:Fixnum:<: “a#{1}b#{2}c”

Thank you for the tracer analysis. I did some time benchmarks and it
seems to be about 30% faster. I agree completely that interpolation is
better.

-Paul

8

On Jun 13, 2012, at 21:28 , Ryan D. wrote:

On Jun 13, 2012, at 21:24 , Paul Sutton wrote:

Easiest is subjective - but yes, I think string interpolation is in
general a better solution when outputting a string.

It is measurable by the number of methods called and the number of garbage
objects created.

Compare:

% ruby -rtracer -e ‘“a” + 1.to_s + “b” + 2.to_s + “c”’
#0:-e:1::-: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:Fixnum:>: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:Fixnum:<: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:>: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:<: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:>: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:<: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:Fixnum:>: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:Fixnum:<: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:>: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:<: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:>: “a” + 1.to_s + “b” + 2.to_s + “c”
#0:-e:1:String:<: “a” + 1.to_s + “b” + 2.to_s + “c”

2111 % ruby -rtracer -e ‘“a#{1}b#{2}c”’
#0:-e:1::-: “a#{1}b#{2}c”
#0:-e:1:Fixnum:>: “a#{1}b#{2}c”
#0:-e:1:Fixnum:<: “a#{1}b#{2}c”
#0:-e:1:Fixnum:>: “a#{1}b#{2}c”
#0:-e:1:Fixnum:<: “a#{1}b#{2}c”