angularjs - 最大化 $digest 迭代

Question

我正在这个 fiddle 中使用指令和 = 绑定(bind)。我收到以下错误:

Uncaught Error: 10 $digest() iterations reached. Aborting!
Watchers fired in the last 5 iterations: [["fn: function () {\n                  var parentValue = parentGet(parentScope);\n\n                  if (parentValue !== scope[scopeName]) {\n                    // we are out of sync and need to copy\n                    if (parentValue !== lastValue) {\n                      // parent changed and it has precedence\n                      lastValue = scope[scopeName] = parentValue;\n                    } else {\n                      // if the parent can be assigned then do so\n                      parentSet(parentScope, lastValue = scope[scopeName]);\n                    }\n                  }\n                  return parentValue;\n                }; newVal: {\"baz\":3}; oldVal: {\"baz\":3}"],["fn: function () {\n                  var parentValue = parentGet(parentScope);\n\n                  if (parentValue !== scope[scopeName]) {\n                    // we are out of sync and need to copy\n                    if (parentValue !== lastValue) {\n                      // parent changed and it has precedence\n                      lastValue = scope[scopeName] = parentValue;\n                    } else {\n                      // if the parent can be assigned then do so\n                      parentSet(parentScope, lastValue = scope[scopeName]);\n                    }\n                  }\n                  return parentValue;\n                }; newVal: {\"baz\":3}; oldVal: {\"baz\":3}"],["fn: function () {\n                  var parentValue = parentGet(parentScope);\n\n                  if (parentValue !== scope[scopeName]) {\n                    // we are out of sync and need to copy\n                    if (parentValue !== lastValue) {\n                      // parent changed and it has precedence\n                      lastValue = scope[scopeName] = parentValue;\n                    } else {\n                      // if the parent can be assigned then do so\n                      parentSet(parentScope, lastValue = scope[scopeName]);\n                    }\n                  }\n                  return parentValue;\n                }; newVal: {\"baz\":3}; oldVal: {\"baz\":3}"],["fn: function () {\n                  var parentValue = parentGet(parentScope);\n\n                  if (parentValue !== scope[scopeName]) {\n                    // we are out of sync and need to copy\n                    if (parentValue !== lastValue) {\n                      // parent changed and it has precedence\n                      lastValue = scope[scopeName] = parentValue;\n                    } else {\n                      // if the parent can be assigned then do so\n                      parentSet(parentScope, lastValue = scope[scopeName]);\n                    }\n                  }\n                  return parentValue;\n                }; newVal: {\"baz\":3}; oldVal: {\"baz\":3}"],["fn: function () {\n                  var parentValue = parentGet(parentScope);\n\n                  if (parentValue !== scope[scopeName]) {\n                    // we are out of sync and need to copy\n                    if (parentValue !== lastValue) {\n                      // parent changed and it has precedence\n                      lastValue = scope[scopeName] = parentValue;\n                    } else {\n                      // if the parent can be assigned then do so\n                      parentSet(parentScope, lastValue = scope[scopeName]);\n                    }\n                  }\n                  return parentValue;\n                }; newVal: {\"baz\":3}; oldVal: {\"baz\":3}"]] angular.js:7729
Scope.$digest angular.js:7729
Scope.$apply angular.js:7894
(anonymous function) angular.js:930
invoke angular.js:2788
bootstrap angular.js:928
angularInit angular.js:904
(anonymous function) angular.js:14397
trigger angular.js:1695
(anonymous function) angular.js:1930
forEach angular.js:110
eventHandler angular.js:1929

为什么会发生这种情况？我认为这与 = 绑定(bind)有关。

Answer 1

这是因为它每次经历摘要循环时都会创建一个全新的对象。 watch 在此 = 数据绑定(bind)中注册，因此每次计算 bar="{baz: 3}" 时都会创建一个新对象，因此它将不同于前一个值，触发另一个摘要循环。最终它会中止，这样它就不会无限循环。请参阅http://docs.angularjs.org/guide/concepts#runtime以获得更彻底的解释。

诀窍是使用不会每次都改变的引用来执行 = 数据绑定(bind)。这通常是通过将其放在指令之外的范围内来完成的。请参阅http://jsfiddle.net/u4BTu/7/