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21 Cards in this Set

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How to print to screen?
"puts <string>"

"p <object>" (also prints object type)
How to output to screen without newline?
print
How to evaluate variable inside double quotes?
use "test #{ variable}"
How to open and close a file?
aFile = File.new("filename", "mode")
# ... process the file
aFile.close
How to read the first 20 characters in a file?
sysread can be used to read the contents of a file

e.g. content = aFile.sysread(20)
how to read the lines of a textfile?
arr = IO.readlines("fileltest.txt")
How to read lines with Ruby?
File.open('test.txt').each_line{ |s|
puts s
}

or

File.foreach('test.txt') { |s|
puts s
}

close file
What is the output?

def callBlock
yield
yield
end


callBlock { puts "In the block" }
In the block
In the block
What does this produce?

a = %w( ant bee cat dog elk ) # create an array
a.each { |animal| puts animal } # iterate over the contents
ant
bee
cat
dog
elk
What is the effect of this?

a = %w{ ant bee cat dog elk }
an array of string with values e.g.

a[0] >> "ant"
a[3] >> "dog"
How do you define a dictionary?
instSection = {
'cello' => 'string',
'clarinet' => 'woodwind',
'drum' => 'percussion',
'oboe' => 'woodwind',
'trumpet' => 'brass',
'violin' => 'string'
}
Give an example of simple iteration over array
{1,2,3].each do | value |
puts value
end
give different ways to create an array with values: vitamins, minerals and chocolates
# Make a list of clues for a game of charades
clues = ['vitamins', 'minerals', 'chocolates']

# Create the same array by splitting on whitespace
clues = %w(vitamins minerals chocolates)

# Create the same array in steps
clues = Array.new
clues << 'vitamins'
clues << 'minerals'
clues << 'chocolates'
how can you pass arguments to a block?
using | arg | in the start of the block
how to match line with regex?
if line =~ /Perl|Python/
puts "Scripting language mentioned: #{line}"
end
how to control flow with if/else in ruby?
if customerName == "Fred" : print "Hello Fred!"
elsif customerName == "John" : print "Hello John!"
elsif customername == "Robert" : print "Hello Bob!"
end
how to access substrings?
string = "this is an example"
==>"this is an example"
value = string[2..6]
==>"is is"
string[11..-1] = "elephant"; string
==>"this is an elephant"
exit
how to loop of i = 0 to 10
for i in (1..10).to_a

....

end
Meta programming:
How to access meta information of a class?
instance_variable_get '@event'
instance_variable_set '@region', 'UK'
instance_variables
5.public_methods
How to create instance variables with introspection?
class Person
def initiliaze(attributes)
attributes.each do | attr, value |
instance_variable_set("@#{attr}", val)
end
end
end

Person.new :name => 'Peter',
:age => '31',
:sex => :male
why are instance variables marked with @ ?
with the mark @ with can identify variables as instance variables and do not need getters and setters