# Deprecated the 'value' parameter of the 'DropdownButtonFormField' constructor

> The `DropdownButtonFormField` constructor parameter `value` has been replaced by the parameter `initialValue`.




:::important
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under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

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随着时间的推移，文档中描述的方案可能会逐渐失效。
通常情况下，我们不会在每次发布新版本时都对这些文档进行同步更新。

The [breaking change index file](/release/breaking-changes)
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[破坏性改动列表](/release/breaking-changes) 
列出了每个版本的文档。

:::


## Summary

The `value` parameter of the [`DropdownButtonFormField`][] constructor was
deprecated in favor of the `initialValue` parameter.

## Context

The `value` parameter of the [`DropdownButtonFormField`][] constructor was used
to initialize [`DropdownButtonFormField.initialValue`][].
Not using the same name was confusing. For example,
developers falsely assumed that setting `value` would change
the current selected value. This was not the case—it
only set the initial value or when the field is reset.

## Description of change

The `value` parameter of the [`DropdownButtonFormField`][] constructor is
deprecated in favor of the parameter named `initialValue`.

## Migration guide

Replace the `value` parameter of the [`DropdownButtonFormField`][] constructor
with the `initialValue` parameter to initialize
[`DropdownButtonFormField.initialValue`][].

Code before migration:

```dart highlightLines=2
DropdownButtonFormField(
  value: 'Yellow',
),
```

Code after migration:

```dart highlightLines=2
DropdownButtonFormField(
  initialValue: 'Yellow',
),
```

## Timeline

Landed in version: 3.35.0-0.0.pre<br>
In stable release: 3.35

## References

API documentation:

- [`DropdownButtonFormField`][]
- [`DropdownButtonFormField.initialValue`][]

Relevant issues:

- [Issue #169983][]

Relevant PRs:

- [Deprecate `DropdownButtonFormField` `value` parameter in favor of `initialValue`][]

[`DropdownButtonFormField`]: https://api.flutter-io.cn/flutter/material/DropdownButtonFormField/DropdownButtonFormField.html
[`DropdownButtonFormField.initialValue`]: https://main-api.flutter-io.cn/flutter/widgets/FormField/initialValue.html
[Issue #169983]: https://github.com/flutter/flutter/issues/169983
[Deprecate `DropdownButtonFormField` `value` parameter in favor of `initialValue`]: https://github.com/flutter/flutter/pull/170805