Script Writing - Using Loops With Lists

Overview

Loops allow you to iterate through objects in a List in various ways. Click on a Loop method listed below to jump to that section and learn more about what it does, the syntax it requires, and  example code. 

• .each Loops
• For Loops
• For-In Loops
• While Loops

.each Loops

• The .each method is applied to any List. The actions specified in the code block are applied to each element in the List.

Syntax

collection.each {element ->
   //Code to execute for each element in the collection
}

Example 1

This example takes a List of Strings and logs the name of each color in the List using interpolation.

List colors = ['red', 'green', 'blue'] as List
colors.each { color -> 
   logger.info("Color: ${color}")
}

Example 2

This example is identical to the first, except  the element name is omitted. Instead, it is used. it can be used when an element is not specified. 

List colors = ['red', 'green', 'blue'] as List
colors.each {
   logger.info("Color: ${it}")
}

For Loops

• For Loops are very similar to While Loops (see below), but with all 3 components specified as arguments.

Syntax

for(variable declaration; expression; Increment) {
   statement #1
   statement #2
   ...
}

Example

• This example sets an integer i with a starting value of 0, specifies that this loop should run so long as i is less than 5, and increments i by 1 after each loop.
• This example will start logging numbers at 0. After each loop, i increases by 1. The last number displayed in the log will be 4 because once i is 5, we no longer meet the condition so the loop stops.

for(int i = 0 as int;i<5;i++){
   logger.info(i.toString())
}

For-In Loops

• For-In Loops allow us to name our elements explicitly before we iterate through them. The actions specified in the code block are applied to each element. 

Syntax

for (element in collection){
    //Code to execute for each element in the collection
}

Example

This example takes a list of integers and logs them using interpolation.

List numbers = [1, 2, 3, 4, 5] as List
for(num in numbers){
   logger.info("Number: ${num}")
}

While Loops

• While Loops allow us to continue a process until a break condition is met. For example, we may want to loop through a set of records until we find a specific value.

Syntax

while(condition){
    statement #1
    statement #2
    ...
}

Example

This example will start logging numbers at 0. After each loop, the count variable increases by 1. The last number displayed in the log will be 4 because once count is 5, we no longer meet the condition, so the loop stops. 

int count = 0 as int
while(count<5){
   logger.info(count.toString())
   count++
}

Related Articles: 

• Script Writing - Working With Lists
• Script Writing - Syntax Rules
• Script Writing - Using VariablesApp Script Example Library