I have a variable. When I do puts var_name I get this hash:
"{\"numConnections\": 163}"
But when I try to get that number 163 from the value numConnections it isn't working. Here is what I am trying:
connections = temp_var["\"numConnections\""]
puts connections.inspect
or:
connections = temp_var["numConnections"]
puts connections.inspect
both of which equally don't work.
Any idea how to extract that 163 from there?
If you have a JSON string, you need to parse it into a hash before you can use it to access its keys and values in a hash-like way. Consider this IRB session:
1.9.3p194 :001 > require 'json'
=> true
1.9.3p194 :002 > temp_var = "{\"numConnections\": 163}"
=> "{"numConnections": 163}"
1.9.3p194 :003 > temp_var.class
=> String
1.9.3p194 :004 > JSON.parse(temp_var)
=> {"numConnections"=>163}
1.9.3p194 :005 > JSON.parse(temp_var)['numConnections']
=> 163
Related
irb> class A; end
=> nil
irb> a=A.new
=> "#<A:0x3094638>"
irb> a.inspect
=> "#<A:0x3094638>"
irb> b=[]
=> []
irb> b.inspect
=> "[]"
How to get memory address of an array object?
Use the method Object#object_id.
Returns an integer identifier for obj. The same number will be returned on all calls to id for a given object, and no two active objects will share an id. #object_id is a different concept from the :name notation, which returns the symbol id of name.
Example :-
Arup-iMac:arup_ruby $ irb
2.1.2 :001 > s = "I am a string"
=> "I am a string"
2.1.2 :002 > obj_id = s.object_id
=> 2156122060
2.1.2 :003 > ObjectSpace._id2ref obj_id
=> "I am a string"
2.1.2 :004 >
I'm using Ruby 2.0 for a Rails project and am having some issues obtaining the element length of an array in the console.
First example
2.0.0-p353 :001 > search = "test"
=> "test"
2.0.0-p353 :002 > search.split
=> ["test"]
2.0.0-p353 :003 > search.length
=> 4
Second example
2.0.0-p353 :001 > search = "testOne, TestTwo"
=> "testOne, TestTwo"
2.0.0-p353 :002 > search.split(/[\s,]+/)
=> ["testOne", "TestTwo"]
2.0.0-p353 :003 > search.length
=> 16
How do I return the element count instead of the character count?
Well, you're not assigning your split array that's why you're seeing the discrepancy.
What you're actually doing is defining a string search and then trying to manipulate that same string.
Try this
testArray = search.split
testArray.size
>> 1
In the first example you are getting the length of the "test" string, not of the ["test"] array. You should assign it to a variable first.
i.e.:
search = "test" # => "test"
array = search.split # => ["test"]
array.length # => 1
IRB and Rails console both have a nice way of outputting symbols that only quote-escapes them when necessary. Some examples:
1.9.3p194 :001 > "#test".to_sym
=> :#test
1.9.3p194 :002 > "#Test".to_sym
=> :#Test
1.9.3p194 :003 > "#123".to_sym
=> :"#123"
1.9.3p194 :004 > "##_test".to_sym
=> :##_test
1.9.3p194 :005 > "test?".to_sym
=> :test?
1.9.3p194 :006 > "test!".to_sym
=> :test!
1.9.3p194 :007 > "_test!".to_sym
=> :_test!
1.9.3p194 :008 > "_test?".to_sym
=> :_test?
1.9.3p194 :009 > "A!".to_sym
=> :"A!"
1.9.3p194 :010 > "#a!".to_sym
=> :"#a!"
How would you do this yourself, so that you could do:
puts "This is valid code: #{escape_symbol(some_symbol)}"
The easiest and best way to do this is via Symbol's inspect method:
1.9.3p194 :013 > puts "This is valid code: #{"#a!".to_sym.inspect}"
This is valid code: :"#a!"
=> nil
1.9.3p194 :014 > puts "This is valid code: #{"a!".to_sym.inspect}"
This is valid code: :a!
You could look at the sym_inspect(VALUE sym) method in string.c in Ruby 1.9.3 that does that, if you're curious.
So, even though you don't need another method to call inspect, this would be the simplest implementation:
def escape_symbol(sym)
sym.inspect
end
Here's my attempt at implementing with a few regexs, although I'd suggest using inspect instead if you can:
def escape_symbol(sym)
sym =~ /^[#a-zA-Z_]#?[a-zA-Z_0-9]*$/ || sym =~ /^[a-z_][a-zA-Z_0-9]*[?!]?$/ ? ":#{sym}" : ":\"#{sym.gsub(/"/, '\\"')}\""
end
Can someone explain what's happening here?
It seems that the placeholding syntax in SQL statement string doesn't work as expected (or, to say it in a different way, it violates the principle of least surprise), and during runtime an unexpected substitution/escaping is done for var2:
ruby-1.9.2-p290 :001 > puts RUBY_VERSION
1.9.2
=> nil
ruby-1.9.2-p290 :002 > require 'ipaddr'
=> true
ruby-1.9.2-p290 :003 > require 'sqlite3'
=> true
ruby-1.9.2-p290 :004 > var1 = Addrinfo.ip("1.2.3.4")
=> #<Addrinfo: 1.2.3.4>
ruby-1.9.2-p290 :005 > var2 = var1.ip_address
=> "1.2.3.4"
ruby-1.9.2-p290 :006 > var3 = "1.2.3.4"
=> "1.2.3.4"
ruby-1.9.2-p290 :007 > var2 == var3
=> true
ruby-1.9.2-p290 :008 > var2 === var3
=> true
ruby-1.9.2-p290 :009 > var2.eql?(var3)
=> true
ruby-1.9.2-p290 :010 > db = SQLite3::Database.open( "test.db" )
=> #<SQLite3::Database:0x00000100bcfce0>
ruby-1.9.2-p290 :011 > db.execute( "SELECT * FROM devices WHERE deviceaddr=?", var2 )
=> []
ruby-1.9.2-p290 :011 > db.execute( "SELECT * FROM devices WHERE deviceaddr=?", var2.to_s )
=> []
ruby-1.9.2-p290 :012 > db.execute( "SELECT * FROM devices WHERE deviceaddr=?", var3 )
=> [["TEST_DEVICE", "1.2.3.4"]]
Without the SQL placeholder it works (but exposes the db to SQL injections!):
ruby-1.9.2-p290 :013 > db.execute( "SELECT * FROM devices WHERE deviceaddr='#{var2}'" )
=> [["TEST_DEVICE", "1.2.3.4"]]
So what is a safe way to make this work?
TL;DR: SQLite uses UTF; convert Addrinfo's 8-bit ASCII output.
One "safe" way is to use force_encoding("UTF-8") on the output from Addrinfo, so:
> var1.ip_address.encoding
=> #<Encoding:ASCII-8BIT>
> var3.encoding
=> #<Encoding:UTF-8>
> db.execute("SELECT * FROM foo WHERE ip=?", var2.force_encoding("UTF-8"))
=> [["1.2.3.4"]]
http://share.findmespot.com/shared/faces/viewspots.jsp?glId=0rEE45o3ERRryMevW5teqS9gkNI
You can do using the string split method. Easiest way.
ruby-1.9.2-p290 :004 > a = 'http://share.findmespot.com/shared/faces/viewspots.jsp?glId=0rEE45o3ERRryMevW5teqS9gkNI'
=> "http://share.findmespot.com/shared/faces/viewspots.jsp?glId=0rEE45o3ERRryMevW5teqS9gkNI"
ruby-1.9.2-p290 :005 > b = a.split('=')[1]
=> "0rEE45o3ERRryMevW5teqS9gkNI"