Function extractHostBindings

packages/compiler/src/jit_compiler_facade.ts:917–951

(
  propMetadata: {[key: string]: any[]},
  sourceSpan: ParseSourceSpan,
  host?: {[key: string]: string},
)

}

function extractHostBindings(
  propMetadata: {[key: string]: any[]},
  sourceSpan: ParseSourceSpan,
  host?: {[key: string]: string},
): ParsedHostBindings {
  // First parse the declarations from the metadata.
  const bindings = parseHostBindings(host || {});

  // Next, loop over the properties of the object, looking for @HostBinding and @HostListener.
  for (const field in propMetadata) {
    if (propMetadata.hasOwnProperty(field)) {
      propMetadata[field].forEach((ann) => {
        if (isHostBinding(ann)) {
          // Since this is a decorator, we know that the value is a class member. Always access it
          // through `this` so that further down the line it can't be confused for a literal value
          // (e.g. if there's a property called `true`).
          bindings.properties[ann.hostPropertyName || field] = getSafePropertyAccessString(
            'this',
            field,
          );
        } else if (isHostListener(ann)) {
          bindings.listeners[ann.eventName || field] = `${field}(${(ann.args || []).join(',')})`;
        }
      });
    }
  }

  // After that check host bindings for errors
  const errors = verifyHostBindings(bindings, sourceSpan);
  if (errors.length) {
    throw new Error(errors.map((error: ParseError) => error.msg).join('\n'));
  }

  return bindings;
}

function isHostBinding(value: any): value is HostBinding {
  return value.ngMetadataName === 'HostBinding';