Conditional Logic and Templates PDF

CONDITIONAL LOGIC AND TEMPLATES OVERVIEW This chapter outlines how to apply conditional logic statements, work with variables, and call and apply templates. OBJECTIVES By the end of this chapter, you will be able to: Add conditional logic to the XSL transformation to exclude or target sp...

CONDITIONAL LOGIC AND TEMPLATES OVERVIEW This chapter outlines how to apply conditional logic statements, work with variables, and call and apply templates. OBJECTIVES By the end of this chapter, you will be able to: Add conditional logic to the XSL transformation to exclude or target specific records. Describe when to use variables, parameters, and named templates. CONDITIONAL LOGIC Recall that you can use XPath predicates to select certain nodes and the element to execute logic for a selected set of nodes. Combining these two concepts allows for conditional processing in XSLT. In addition to this approach, XSLT also provides conditional logic statements. This functionality may be familiar to traditional software developers. CONDITIONAL LOGIC ELEMENTS You can implement conditional logic in your XSLT transformations by using elements such as , , , and. These elements allow you to apply different transformation rules based on conditions evaluated against the inout XML data. Element: Description: Executes only when the contents of the statement test true. Element: Description: Used within an < xsl:choose> element to indicate one of a number of choices. Element: Description: Used within an < xsl:choose> element to indicate the default action if none of the other choices matches. Element: Description: Used to define multiple conditional branches, similar to an if-else statement in traditional programming. It contains one or more elements and optionally one element. IF VS. CHOOSE STATEMENTS Choose statements allow multiple checks, but only one operation performs for the first instance that tests to true. If statements are tested independently, and each instance that tests to true will have output. COMMON OPERATORS FOR TEST EXPRESSIONS XSLT test expressions are XPath expressions and can include a variety of operators: Comparison Operators: =, !=, = Logical Operators: and, or Functions: XPath functions such as contains(), starts-with(), not(), and others can be used within test expressions. EXAMPLES OF CONDITIONAL LOGIC AND OPERATORS For examples of applying conditional logic, consider the following XML file. The file contains employee information including name, department, and salary. John Doe Finance 45000 Jane Smith HR 50000 Bob Johnson IT 60000 If Statement Example In this example, we use an statement to output "High Earner" if an employee has a salary greater than $50,000. High Earner Choose Statement Example In this example, we use an statement to output a role for each employee based on their department. If the department does not match any of the specified cases, the output defaults to Staff. Accountant HR Specialist Developer Staff Choose Statement with Conditional Operator In this example, we add conditional operators to enhance an statement. If an employee is in the finance department and has a salary greater than $55,000, the role output will be Senior Accountant. If an employee is in either the HR or IT departments, the role output will be Admin Staff. For all other conditions, the role output defaults to General Staff. Senior Accountant Admin Staff General Staff VARIABLES In XSLT, variables store values that you can reference throughout your style sheet. This allows you to create more dynamic and readable transformations. Variables can hold string values, numbers, boolean values, node sets, or result tree fragments. DECLARING VARIABLES You can declare variables globally (at the top level of the style sheet) or locally (within a template, function or another XSLT element). Declare variables in XSLT using the element: The element includes a name attribute and an optional select attribute. Attribute: name Definition: Specifies the name of the variable. Variable names must be unique within their scope. Attribute: select (Optional) Definition: An XPath expression that evaluates to the value of the variable. If omitted, the content of the element is also the value. CALLING VARIABLES To call a variable in XSLT, use the $ symbol with the variable name: VARIABLE BENEFITS Effectively using variables can help you write more efficient XSLT style sheets. Variables are beneficial because they allow you to: Store values for expressions that are reused multiple times, reducing redundancy. Give meaningful names to complex expressions, making the style sheet easier to read and maintain. Avoid repeated evaluation of complex XPath expressions, which can improve performance. VARIABLE LIMITATIONS When using variables in XSLT, keep the following limitations in mind: Variables in XSLT are immutable. Once you set a variable, its value cannot be changed. Global variables are accessible everywhere, while local variables are limited to the scope they are defined in. Local variables can hide global variables with the same name within their scope. GLOBAL VARIABLE EXAMPLE Consider the following XSLT. In this example, company is a global variable declared at the top of the style sheet. Because this variable is declared outside of any templates, it is accessible throughout the entire stylesheet. create 25 multichoice questions with answer immediately after the question. put a pipe sign at the end of every line. the questions need to based on this text: CALLING NAMED TEMPLATES The element calls a named template. This is similar to calling a function in traditional programming. Named templates provide code blocks that you can reuse multiple times within the style sheet. SYNTAX Define named templates with a name attribute. The name attribute specifies the name of the template to call. EXAMPLE In this example, the template matching the root element applies templates to each employee element. Each employee element calls the named template, formatEmployee, to format its details.