String helpers

Add and test string processing methods.

The slugify method

We'll write a slugify method to turn a string into a URL-friendly form. The method lowercases the letters and replaces spaces with hyphens; this makes titles or tags fit for links.

Example: 'Hello World'.toLowerCase().replaceAll(' ', '-') gives 'hello-world'. We'll add this as a String slugify(String text) method on the class. In Dart toLowerCase lowercases letters and replaceAll replaces the first argument with the second. The same shape works for titles, tags and file names.

Method chaining

slugify calls two methods back to back: first toLowerCase(), then replaceAll(...). This method chaining passes the result of each method to the next.

Example: text.toLowerCase().replaceAll(' ', '-'). Here toLowerCase() returns a lowercase String and replaceAll(...) works on that String. The chain can be longer: text.toLowerCase().trim().replaceAll(' ', '-'). Each step applies to the previous result. This shape is a concise way to transform data step by step.

Exercise Add slugify to Helper

Keep the existing Helper class. Add a String slugify(String text) { return text.toLowerCase().replaceAll(' ', '-'); } method to the class. In main, create an instance with var h = Helper(); and call print(h.slugify('Hello World')).

Show example solution

class Helper {
  final String version;
  Helper() : version = '1.0';
  String slugify(String text) {
    return text.toLowerCase().replaceAll(' ', '-');
  }
}

void main() {
  var h = Helper();
  print(h.slugify('Hello World'));
}

Test yourself

What does slugify('Hello World') return?
- HelloWorld
- hello-world
- hello_world
- HELLO WORLD
Show answer

hello-world — toLowerCase lowercases, replaceAll(' ', '-') turns spaces into hyphens.

Complete the slugify body

  String slugify(String text) {
    return text.____(' ', '-');
  }

Show answer

  String slugify(String text) {
    return text.replaceAll(' ', '-');
  }

Match the slugify parts

slugify

Method name
toLowerCase

Lowercases letters
replaceAll

Turns spaces into hyphens

Next lesson: Number helpers

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