Search the Library

public List<Book__c> searchBooks(String searchTerm) {
    List<List<sObject>> searchResults = [
        FIND :searchTerm IN ALL FIELDS
        RETURNING Book__c(Id, Title__c, Author__c, Is_Checked_Out__c)
    ];

    return (List<Book__c>) searchResults[0];
}

This is Module 21's SOSL search pattern, applied directly: FIND :searchTerm IN ALL FIELDS matches the term against Title__c, Author__c, and any other searchable text field on Book__c at once — one search covering both title and author lookups a user might type.

LibraryService library = new LibraryService();
List<Book__c> results = library.searchBooks('Bachman');

for (Book__c book : results) {
    System.debug(book.Title__c + ' by ' + book.Author__c);
}

A member typing "Bachman" into a search box finds every book by that author — even though the search term matched Author__c, not Title__c — without the search code needing to know in advance which field the match would come from.

// The SOQL alternative would need two separate queries and merged results
List<Book__c> byTitle = [SELECT Id, Title__c FROM Book__c WHERE Title__c LIKE :('%' + searchTerm + '%')];
List<Book__c> byAuthor = [SELECT Id, Title__c FROM Book__c WHERE Author__c LIKE :('%' + searchTerm + '%')];
// ...then manually merge and deduplicate the two lists

Module 21's core lesson applies directly: SOSL naturally searches multiple fields (and, if needed later, multiple objects) in one statement, avoiding the manual merging and deduplication a SOQL-only approach would require here.