Tropical Software Observations

16 October 2012

Posted by Jun Rong

at 3:16 PM


Ruby Block vs vs Lambda vs method(:func) Summarized

There are many ways to pass code around in Ruby, so today I'm going to make a comparison between the 4 different ways. The first section, I will show the syntax of using each of them:
1. Block
2. Proc
3. Lambda
4. method(:func)
On the second section, I will compare the subtle differences they have.

A quick syntax comparison:
* note that the result is at the last section of each code *
1. Block
3. Lambda
4. method(:some_method)

Discussion on the subtle differences:
The table below summarizes what each of them can and cannot do, under the table, there are a more in depth explanation on the things shown in the table.
Description Block Proc Lambda Method Proof
Storing into a variable No Yes Yes Yes See (a)
How they work N/A Code Replacement Method Call Method Call See (b)
What class they belong to Proc Proc Proc Method See (c)
Check for correct number of argument No No Yes Yes See (d)

(a) Storing into a variable
Only block is not able to be stored into a variable, the rest is possible, refer to the quick syntax section above.

(b) How they work
Referring to the code right above this sentence, we can see that for proc_return, the line return "proc2 I AM HERE!" is never executed, this is because,{return "proc1}.call works like code replacement, we can imagine proc_return to be like this:

(c) What class they belong to
Run this code: (d) Check for correct number of argument
Block and Proc don't check for the correct number of arguments, they discard extra parameters silently.( For lambda and method(:func), they give error right away. Here's the code
For block:
For proc:
For lambda:
For method(:func):