DataWeave Delight: Padding strings

In DataWeave we can create a fixed width string value. If the string value is less than the fixed width than the space is padded with spaces or any other character we want. We can add the padding to the left of our string value or to the right. For left padding we use the function leftPad from the dw::core::Strings module. And for right padding we use the function rightPad in the same module. The functions takes as first argument the string value, the second argument is the total width of the resulting string and the third optional argument is the character we want to use for padding. By default the padding character is a space (" "), but we can use any character. We must make sure we only use 1 character, because when we use more than 1 character the result is no longer a string value with our defined maximum width.

In the following example we use both functions with several arguments:

Source

%dw 2.0

import rightPad, leftPad from dw::core::Strings

var text = "DataWeave"

output text/plain
---
"|$(text)|
|$(rightPad(text, 12))| 
|$(rightPad(text, 12, "*"))|
|$(leftPad(text, 12))|
|$(leftPad(text, 12, "-"))|

Using multiple characters for padding 
gives unexpected result:
|$(rightPad(text, 12, " * "))| 
"

Output

|DataWeave|
|DataWeave   | 
|DataWeave***|
|   DataWeave|
|---DataWeave|

Using multiple characters for padding 
gives unexpected result:
|DataWeave *  *  * | 

In the following example we use the leftPad and rightPad functions to generate a report as text.

%dw 2.0

import rightPad, leftPad from dw::core::Strings

var data = [
    { page: "page1.html", responseTime: 200, size: 1201 },
    { page: "page2.html", responseTime: 42,  size: 8853 },
    { page: "page3.html", responseTime: 98,  size: 3432 },
    { page: "page4.html", responseTime: 432, size: 9081 },
]

fun total(index) = data reduce ((row, result = 0) -> result + row[index] as Number)

var totalTime = total(1)
var totalSize = total(2)

output text/plain
---
"
*** Summary ***

$(rightPad("Total pages", 25)): $(leftPad(sizeOf(data) as String, 6))
$(rightPad("Total response time (ms)", 25)): $(leftPad(totalTime as String, 6))
$(rightPad("Total size (KB)", 25)): $(leftPad(totalSize as String, 6))

*** Details ***

$(data map ((item) -> rightPad(item.page, 14) ++ 
                      leftPad(item.responseTime, 5) ++ 
                      leftPad(item.size, 8)) 
       joinBy "\n")
"

Output

*** Summary ***

Total pages              :      4
Total response time (ms) :    772
Total size (KB)          :  22567

*** Details ***

page1.html      200    1201
page2.html       42    8853
page3.html       98    3432
page4.html      432    9081

Written with DataWeave 2.4.