Strings recipes for the Dart Cookbook

recipes/test/core/strings/incrementally_building_test.dart

+library incrementally_building;
+
+import 'package:unittest/unittest.dart';
+
+var data = [{'scheme': 'https', 'domain': 'news.ycombinator.com'}, 
+            {'domain': 'www.google.com'}, 
+            {'domain': 'reddit.com', 'path': 'search', 'params': 'q=dart'}
+            ];
+
+String assembleUrlsUsingStringBuffer(data) {
+  StringBuffer sb = new StringBuffer();
+  for (final item in data) {
+    sb.write(item['scheme'] != null ? item['scheme']  : 'http');
+    sb.write("://");
+    sb.write(item['domain']);
+    sb.write('/');
+    sb.write(item['path'] != null ? item['path']  : '');
+    if (item['params'] != null) {
+      sb.write('?');
+      sb.write(item['params']);
+    }
+    sb.write('\n');
+  }
+  return sb.toString();
+}
+
+String assembleUrlsUsingConcat(data) {
+  var urls = '';
+  for (final item in data) {
+    urls = urls.concat(item['scheme'] != null ? item['scheme']  : 'http');
+    urls = urls.concat("://");
+    urls = urls.concat(item['domain']);
+    urls = urls.concat('/');
+    urls = urls.concat(item['path'] != null ? item['path']  : '');
+    if (item['params'] != null) {
+      urls = urls.concat('?');
+      urls = urls.concat(item['params']);
+    }
+    urls = urls.concat('\n');
+  }
+  return urls;
+}
+
+void main() {
+  group('incrementally building a string', () {
+    group('using a StringBuffer', () {
+      test('using write()', () {
+        expect(assembleUrlsUsingStringBuffer(data), equals('''https://news.ycombinator.com/
+http://www.google.com/
+http://reddit.com/search?q=dart
+'''));
+    });
+      test('using several methods', () {
+        var sb = new StringBuffer();
+        sb.writeln('The Beatles:');
+        sb.writeAll(['John, ', 'Paul, ', 'George, and Ringo']);
+        sb.writeCharCode(33); // charCode for '!'.
+        expect(sb.toString(), equals('The Beatles:\nJohn, Paul, George, and Ringo!'));
+      });
+    });
+    
+    group('using concat()', () {
+      test('', () {  
+        expect(assembleUrlsUsingConcat(data), equals('''https://news.ycombinator.com/
+http://www.google.com/
+http://reddit.com/search?q=dart
+'''));
+      });
+    });
+  });
+}