registerPattern method

void registerPattern(String method, Pattern pattern, RequestHandler handler)

Register a request handler for any HTTP method with a Pattern.

This method is used if the caller already has a Pattern object. Usually, an application will have the pattern as a String, in which case it can use the register method instead, which simply converts that string into a Pattern object and then invokes this method.

Throws a DuplicateRule if there is a conflict with an existing rule. A conflict is if Pattern.matchesSamePaths is true for the two patterns.

Implementation

void registerPattern(String method, Pattern pattern, RequestHandler handler) {
  if (method.isEmpty) {
    throw ArgumentError.value(method, 'method', 'Empty string');
  }

  _logServer.config('register: $method $pattern');

  // Get the list of rules for the HTTP method

  var methodRules = _rulesByMethod[method];
  if (methodRules == null) {
    methodRules = []; // new List<ServerRule>();
    _rulesByMethod[method] = methodRules;
  }

  // Check if another rule already exists with the "same" pattern.
  // It is an error if one exists.
  //
  // It is not an error to have two rules that match a path. The order
  // of those rules will determine which one matches, and there can be other
  // paths that match one and not the other. So both have a purpose.
  //
  // But it is an error to have two rules with the "same" pattern. With them,
  // the first rule will always match, and there are no paths which will
  // not match one and match the other. So one of them is redundant. If it
  // was allowed, one of them will never get used.

  final newRule = ServerRule(pattern.toString(), handler);

  try {
    final existingRule = methodRules
        .firstWhere((sr) => sr.pattern.matchesSamePaths(newRule.pattern));

    // A rule with the "same" pattern already exists: cannot add it
    throw DuplicateRule(method, pattern, handler, existingRule.handler);

    // ignore: avoid_catching_errors
  } on StateError {
    // A rule with the "same" pattern does not exist: success: record the rule
    methodRules.add(newRule);
  }
}