Bracketology brak'itol'je

1
Bracketology(brak'it-ol'?-je)
-noun 1. The science of efficiently using
brackets in ltCFMLgt

• Brian Love
• Hamilton College
• Web Integration Specialist

2
Bracketology (brak'it-ol'?-je)

• Overview
• What is this bracket thing all about?
• Object.property notation
• Associative array notation
• How it all works
• Embedding brackets
• Mixing it up
• Avoiding Evaluate()
• Looping over arrays, structures, and queries
• Using brackets with objects

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Bracketology (brak'it-ol'?-je)

• Everything is ColdFusion is a structure (scoped)
• Variables (and this scope)
• Form
• Url
• Cgi
• Cookie
• Client, Cookie, and Session
• Application
• Server
• We can refer to complex structures using two
  methods
• object.property notation
• Associative array notation

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Object.property notation

• Sometimes referred to as dot notation
• Example

ltcfscriptgt mystr StructNew() mystr.key1
ColdFusion rocks mystr.key2 CF makes
coding fun lt/cfscriptgt ltcfoutputgt Key 1
value mystr.key1 ltbr /gt key 2 value
mystr.key2 lt/cfoutputgt
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Associative Array notation

• What the heck is the associative array stuff all
  about?
• Definition by Wikipedia
• An associative array is an abstract data type
  composed of a collection of keys and a collection
  of value, where each key is associated with one
  value.

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Associative Array notation

• By using brackets we can perform the following
  operations on structures in ColdFusion
• Add binding a new key to a new value
• Lookup Find the value that is bound to a key

ltcfset myStr StructNew()gt ltcfset myStrkey1
value 1gt
ltcfoutputgt myStrkey1 lt/cfoutputgt
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How does it work?

• Anything inside of the brackets must be a valid
  ColdFusion expression
• Basically, think of it like cfset
• What is inside of the bracket is the right side
• Since the variable i is 1, myVar will be set to
  guest1
• The difference Instead of returning the value to
  a variable (in this case, myVar), the value is
  returned to the whole expression to be evaluated
  (and then acted upon)

ltcfset i 1gt ltcfset myVar guest i gt
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Embedding brackets

• No limit to the number of embedded
• Brackets are evaluated from the inside out

variablesbracketswithinbrackets
3
1
variablesbracketswithinbrackets
2
4
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Working from the inner-most out

• So, first we have the whole expression
• Then, the inner-most bracket is evaluated
• Then, the entire expression is evaluated (after
  all brackets have been evaluated)

ltcfset i 1gt ltcfoutputgt formguesti
lt/cfoutputgt
ltcfoutputgt formguest1 lt/cfoutputgt
ltcfoutputgt form.guest1 lt/cfoutputgt
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Brackets are expressions
ColdFusion expressions consist of operands and
operators.
Operands are comprised of constants and variables

• So, what is in between the brackets, must be a
  valid ColdFusion expression.
• Most common uses
• VariablesmyVar something myVar2
• VariablesmyVarsomethingmyVar2

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Bracketology example 1

• A structure containing account numbers
• A query that is a transaction log
• Lets find out the ending balance for each account
  and store the results in a structure

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Mixing it up

• ColdFusion also allows you to mix both
  object.property notation with associative array
  notation

ltcfscriptgt myStr StructNew() myStrkey1
value 1 myStrkey2 ArrayNew(1)
myStr.key21 Array value 1 myStr.key2.2
Array value 2 lt/cfscriptgt
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Do you do this
ltform ...gt ltcfloop from1 to10 indexigt
ltcfinput nameguesti ...gt
lt/cfloopgt lt/formgt
..And then
ltcfloop from1 to10 indexigt ltcfoutputgt
Evaluate(guesti) lt/cfoutputgt lt/cfloopgt
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Avoiding Evaluate()
You can concatenate the string guest with the
variable i
ltcfloop from1 to10 indexigt ltcfoutputgt
formguesti lt/cfoutputgt lt/cfloopgt
Or, you can evaluate the string guesti
ltcfloop from1 to10 indexigt ltcfoutputgt
formguesti lt/cfoutputgt lt/cfloopgt
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Timing Evaluate()
Test performed using CF8 Developer Edition with
CFTIMER running in standard mode with built-in
web server on Windows Vista Ultimate platform
with 2.80 GHz Pentium D and 2046MB RAM.
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Looping over arrays

• We can easily loop over the elements of a
  ColdFusion array using brackets and the for loop

ltcfscriptgt myArray value 1, value 2,
value 3 //loop over array and output to
browser for(i1 i lt ArrayLen(myArray) i)
WriteOutput(myArrayi ltbr /gt)
lt/cfscriptgt
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Looping over structures

• We can loop over the elements in a ColdFusion
  structure using brackets and the for-in loop

ltcfscriptgt myStr StructNew() myStrkey1
value 1 myStr.key2 value 2 //loop
over struct and output to browser for(key in
myStr) WriteOutput(myStrkey ltbr /gt)
lt/cfscriptgt
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Looping over queries

• We can easily loop over the elements of a
  ColdFusion query object using brackets and the
  for loop

ltcfscriptgt myQry QueryNew("values") for
(i1 i lte 3 i) QueryAddRow(myQry)
QuerySetCell(myQry,"values","Query value "i)
//loop over array and output to browser
for(i1 i lt myQry.recordcount i)
WriteOutput(myQry'values'i 'ltbr /gt')
lt/cfscriptgt
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Using brackets with objects

• We have a CFC with a generic setter and getter,
  i.e.
• userObj.get(name)
• If defined, we would like to call a custom getter
  function, i.e.
• userObj.get(name) will in turn call
• getCustomName() that will return the value.

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Using brackets with objects

• We can use bracket notation to reference the
  custom function like this

ltcfcomponent nameusergt ltcffunction name"get"
output"false" access"public"gt ltcfargument
name"field" required"yes" /gt ltcfset var
newfuncname "" /gt ltcfif
structkeyexists(variables,'getarguments.field')
AND isCustomFunction(variables'get'argumen
ts.field)gt ltcfset newfuncname
variables'get'arguments.field /gt
ltcfreturn newfuncname() /gt lt/cfifgt
return value from data struct
lt/cffunctiongt lt/cfcomponentgt
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Thank youPresentation Examples available at
brianflove.com

• Brian Love
• Hamilton College
• Web Integration Specialist