FormControlNamelink

说明link

This directive ensures that any values written to the FormControl instance programmatically will be written to the DOM element (model -> view). Conversely, any values written to the DOM element through user input will be reflected in the FormControl instance (view -> model).

该指令会确保通过程序写入到该 FormControl 实例的任何值都会被写入到 DOM 元素上（模型 -> 视图）。 反过来，任何通过用户输入写入 DOM 元素上的值也会被反映到这个 FormControl 实例上（视图 -> 模型）。

This directive is designed to be used with a parent FormGroupDirective (selector: [formGroup]).

该指令旨在与父级 FormGroupDirective（选择器：[formGroup]）协同使用。

It accepts the string name of the FormControl instance you want to link, and will look for a FormControl registered with that name in the closest FormGroup or FormArray above it.

它接受一个想要链接的 FormControl 实例的字符串名称，它会在最近的父级 FormGroup、FormArray 上根据该名称查找这个 FormControl。

Access the control: You can access the FormControl associated with this directive by using the get method. Ex: this.form.get('first');

访问控件：你可以使用 get 方法访问与此指令关联的FormControl。 例如：this.form.get('first');

Get value: the value property is always synced and available on the FormControl. See a full list of available properties in AbstractControl.

获取值：这个 value 属性会一直和这个 FormControl 保持同步，并一直可用。 参见 AbstractControl 的所有可用属性的列表。

Set value: You can set an initial value for the control when instantiating the FormControl, or you can set it programmatically later using setValue or patchValue.

设置值：当初始化 FormControl 时，可以为该控件设置一个初始值； 或者稍后也可以使用 setValue 或 patchValue 来通过代码设置它。

Listen to value: If you want to listen to changes in the value of the control, you can subscribe to the valueChanges event. You can also listen to statusChanges to be notified when the validation status is re-calculated.

监听值的变化：如果想监听控件值的变化，你可以订阅 valueChanges 事件。 你还可以监听 statusChanges 以便在验证状态重新计算时得到通知。

Examplelink

例子link

In this example, we create form controls for first name and last name.

在这个例子中，我们为名和姓创建了两个表单控件。

To see formControlName examples with different form control types, see:

要查看把 formControlName 应用于不同类型的表单控件的例子，参见：

• Radio buttons: RadioControlValueAccessor

  单选按钮: RadioControlValueAccessor

• Selects: SelectControlValueAccessor

  单选下拉框: SelectControlValueAccessor

npm package: @angular/forms

npm 包: @angular/forms

NgModule: ReactiveFormsModule

Use with ngModellink

和 ngModel 一起使用link

Support for using the ngModel input property and ngModelChange event with reactive form directives has been deprecated in Angular v6 and will be removed in Angular v7.

从 Angular v6 开始，已经废弃了在响应式表单中使用使用输入属性 ngModel 和事件 ngModelChange 的方式，并将在 Angular v7 中移除。

Now deprecated:

现已废弃：

This has been deprecated for a few reasons. First, developers have found this pattern confusing. It seems like the actual ngModel directive is being used, but in fact it's an input/output property named ngModel on the reactive form directive that simply approximates (some of) its behavior. Specifically, it allows getting/setting the value and intercepting value events. However, some of ngModel's other features - like delaying updates withngModelOptions or exporting the directive - simply don't work, which has understandably caused some confusion.

它被废弃有几个理由。 首先，一些开发者觉得这种用法让人困惑。它看起来好像是在使用 ngModel 指令， 但实际上它只是响应式表单指令上的一个名叫 ngModel 的输入/输出属性，只是在行为上和 ngModel 指令有点相似而已。 特别是，它运行获取 / 设置控件值，并拦截值变更事件。 不过，不支持 ngModel 的某些其它特性 - 比如不能用 ngModelOptions 进行延迟修改，也不能导出该指令， 如果没有理解这一点，就会带来一些困惑。

In addition, this pattern mixes template-driven and reactive forms strategies, which we generally don't recommend because it doesn't take advantage of the full benefits of either strategy. Setting the value in the template violates the template-agnostic principles behind reactive forms, whereas adding a FormControl/FormGroup layer in the class removes the convenience of defining forms in the template.

此外，该模式混用了模板驱动表单和响应式表单的策略，我们通常不建议这么实用，因为它无法同时得到这两种策略的全部优点。 在模板中设置值，违背了响应式表单背后的 "模板无关性" 设计原则；而在类中增加 FormControl/FormGroup 层次则破坏了在模板中定义表单带来的便利性。

To update your code before v7, you'll want to decide whether to stick with reactive form directives (and get/set values using reactive forms patterns) or switch over to template-driven directives.

要在 Angular v7 之前修改你的现有代码，就要决定是钉死在响应式表单指令（并通过响应式表单模式来获取/设置值）或切换到那些模板驱动表单的指令。

After (choice 1 - use reactive forms):

以后的写法（选择 1 - 使用响应式表单）：

After (choice 2 - use template-driven forms):

以后的写法（选择 2 - 使用模板驱动表单）：

By default, when you use this pattern, you will see a deprecation warning once in dev mode. You can choose to silence this warning by providing a config for ReactiveFormsModule at import time:

默认情况下，当你使用此模式时，你会在开发模式下看到一个废弃（deprecation）警告。 你可以在导入 ReactiveFormsModule 时提供一个配置项来消除这个警告：

Alternatively, you can choose to surface a separate warning for each instance of this pattern with a config value of "always". This may help to track down where in the code the pattern is being used as the code is being updated.

或者，你也可以选择指定一个配置值 "always" 来为每个符合这种模式的实例都单独显示一个警告。 这会帮助你在修改代码时追踪代码中用到这种模式的所有位置。