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Archive for the 'mini-saga' Category
16Feb09 Why ||=?
mini-saga programming ruby
0 Comments

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||= is a very useful technique in Ruby programming and is used like:

  |  copy code |? 
1
x ||= 5

It relies on nil evaluating as false. It works like this: a variable is equal to its value xor some other value. If the variable is nil, then the other value is used. Otherwise, it keeps its value.

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01
irb(main):001:0> x ||= 5
02
=> 5
03
irb(main):002:0> x
04
=> 5
05
irb(main):003:0> y=2
06
=> 2
07
irb(main):004:0> y ||= 7
08
=> 2
09
irb(main):005:0> z
10
NameError: undefined local variable or method `z' for main:Object
11
        from (irb):5
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        from :0
13
irb(main):006:0> z=nil
14
=> nil
15
irb(main):007:0> z ||= 3
16
=> 3
17
irb(main):008:0> m
18
NameError: undefined local variable or method `m' for main:Object
19
        from (irb):8
20
        from :0
21
irb(main):009:0> m ||= 1
22
=> 1
23
irb(main):010:0>

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15Feb09 It went (that) way
mini-saga programming ruby
0 Comments

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Logical and arithmetic rotate one bit left
Image via Wikipedia

Ruby supports operator overloading — operators behave as methods of an object. So, << behaves differently based on the context. Generally for anything other than bit shifting << means to append or concatenate, such as with a string or an array. Concatenate is generally faster than addition — new objects are not created.

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1
matt:~$ irb
2
>> 32 << 3
3
=> 256
4
>> "cat" << 'nip'
5
=> "catnip"
6
>> [0,2] << 2
7
=> [0, 2, 2]

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14Feb09 Open-uri makes for developer friendly I/O
mini-saga programming ruby
0 Comments

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A Venn diagram of Uniform Resource Identifier ...
Image via Wikipedia

open-uri, a part of the standard Ruby distribution, makes opening and reading from a URI easy. With it, developers use familiar methods like open for performing I/O with URI’s.

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1
require 'open-uri'
2
open("http://www.ruby-lang.org/") {|f|
3
    f.each_line {|line| p line}
4
}
5


Contrast Net::HTTP which uses numerous methods to achieve the same effect.


  |  copy code |? 
1
require 'net/http'
2
 
3
url = URI.parse('http://www.example.com/index.html')
4
req = Net::HTTP::Get.new(url.path)
5
res = Net::HTTP.start(url.host, url.port) {|http|
6
  http.request(req)
7
}
8
puts res.body
9


An addon, SuperIO, adds more flexiblity in attempting to DTRT.


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								13Feb09								
																
								More on Mini-Sagas								
							

				
							

								administrivia mini-saga								

									0 Comments								

															

						
					

					
				

				
				
				
			

			
			

			
			
				

					
While I’ve decided to limit the Mini Sagas to 50 words, I’ve decided to not count the words in code snippets.   Why?  I’ve written one and the 50 word limit, when code snippets are included is too constraining.  It was extremely vague and didn’t begin to explain what was necessary.

										
										
				

				
			

			
			

		

		
	

	
	

    
	

			
	

		

		
		
			
			


		
					


											
							

							
							

																
								13Feb09								
																
								Holy Ruby Methods, Batman!								
							

				
							

								mini-saga programming ruby								

									0 Comments								

															

						
					

					
				

				
				
				
			

			
			

			
			
				

					
bang!Conventions are one of Ruby‘s nicest features, making it easier to read and maintain.   One convention is that methods which may modify an object have a ‘!’ in their name, such as ‘chop!’,  which indicates if there are no changes, then nil is returned.   This can cause issues with method chaining.


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