MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuale Utente Scaricare il pdf (Pagina 39)

39Returning Structures from CFX Tags

Returning Structures from CFX Tags

As you probably already know, ColdFusion supports a feature referred to in the documentation as

Smart Structs. The idea behind the Smart Structs feature is to make it easier to construct complex

data structures in CFML code. Basically, if you use

<cfset> or some other mechanism to create a

variable, and the variable name contains dots or square brackets such that the new variable would be

nested within a structure of structures, ColdFusion will automatically create any intermediary

structures necessary to allow the

<cfset> to execute without errors.

To illustrate, consider the following line:

This line will execute successfully even if the OrangeWhip structure does not exist yet. The same goes

for the

Actresses or HotList parts.

CFX Tags Are Smart, Too

So what does this have to do with CFX tags? It turns out that the CFX interface uses the same

internal functions within the ColdFusion server to set variables. So, if you supply a variable name

that contains dots to

response.setVariable() (in Java) or Request->SetVariable() (in C++),

ColdFusion will automatically create the intermediary structures needed to set the variable with

the name you specify.

For instance, the code listings for this chapter include a ﬁle called Request2.cpp, which contains the

source code for a new CFX tag called

<CFX_ComputeStatistics>. This listing is very similar to the

<CFX_ComputeStandardDeviation> tag created earlier in this chapter and takes the same attributes.

The difference is that instead of returning a single number, it returns a structure with ﬁve keys (values)

named StandardDeviation, Variance, Mean, Sum, and Count (the number of non-null data points).

Figure 30.11

CFX tags can include

debugging messages if

unexpected conditions

arise.

1 2 ... 34 35 36 37 38 39 40 41 42 43 44

Nessun commento

MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuale Utente Pagina 39