---
title: 读取和写入数据
slug: docs-ch/get-started/read-and-write-data
description: 了解如何在 Back4App 上使用 Parse SDK 执行数据操作，包括 CRUD。
image: https://www.back4app.com/_public/img/back4app-og.png
createdAt: 2024-01-23T18:25:46.036Z
---

本指南将教您如何 **创建、读取、更新和删除** 在 Back4app 上使用 Parse SDK 的数据对象。Back4app 的数据存储围绕着 `Parse.Object` 类展开，该类允许您存储 JSON 兼容数据的键值对，提供灵活性和简便性的数据管理。

## 目标

- 了解如何在 Back4app 上使用 Parse SDK 执行数据操作（CRUD）。
- 学习如何在不同平台上设置和使用 Parse SDK。

## 先决条件

:::hint{type="info"}
**在 Back4app 上的应用程序**: 您需要在 Back4app 上创建一个应用程序。

- [创建新应用程序的指南](https://www.back4app.com/docs/get-started/new-parse-app).

**Parse SDK 安装**:

- [Parse SDK 安装指南](https://www.back4app.com/docs/get-started/parse-sdk).
:::

## 1 - 创建 Parse 对象

要在 Back4app 中存储数据，您需要创建一个 `ParseObject` 与特定类相关联。例如，在一个与足球相关的应用程序中，您可以创建一个 `SoccerPlayers` 类来存储有关球员的数据。

:::CodeblockTabs
```javascript
async function saveNewPlayer() {
  const soccerPlayers = new Parse.Object("SoccerPlayers");
  soccerPlayers.set("playerName", "A. Wed");
  soccerPlayers.set("yearOfBirth", 1997);
  soccerPlayers.set("emailContact", "a.wed@email.io");
  soccerPlayers.set("attributes", ["fast", "good conditioning"]);

  try {
    const result = await soccerPlayers.save();
    console.log('New object created with objectId: ' + result.id);
  } catch (error) {
    console.error('Error: ' + error.message);
  }
}
```

Flutter

```dart
ParseObject soccerPlayers = ParseObject('SoccerPlayers')
  ..set('playerName', 'A. Wed')
  ..set('yearOfBirth', 1997)
  ..set('emailContact', 'a.wed@email.io')
  ..set('attributes', ['fast', 'good conditioning']);

ParseResponse response = await soccerPlayers.save();
if (response.success) {
  print('New object created with objectId: ${response.result.objectId}');
} else {
  print('Error: ${response.error.message}');
}
```

Android

```java
ParseObject soccerPlayers = new ParseObject("SoccerPlayers");
soccerPlayers.put("playerName", "A. Wed");
soccerPlayers.put("yearOfBirth", 1997);
soccerPlayers.put("emailContact", "a.wed@email.io");
soccerPlayers.put("attributes", Arrays.asList("fast", "good conditioning"));

soccerPlayers.saveInBackground(e -> {
  if (e == null) {
    Log.d("Parse", "New object created with objectId: " + soccerPlayers.getObjectId());
  } else {
    Log.e("ParseError", e.getMessage());
  }
});
```

iOS

```swift
let soccerPlayer = ParseObject(className: "SoccerPlayers")
soccerPlayer["playerName"] = "A. Wed"
soccerPlayer["yearOfBirth"] = 1997
soccerPlayer["emailContact"] = "a.wed@email.io"
soccerPlayer["attributes"] = ["fast", "good conditioning"]

soccerPlayer.save { result in
    switch result {
    case .success(let savedPlayer):
        print("New object created with objectId: \(savedPlayer.objectId!)")
    case .failure(let error):
        print("Error: \(error.localizedDescription)")
    }
}
```

PHP

```php
$soccerPlayers = new ParseObject("SoccerPlayers");
$soccerPlayers->set("playerName", "A. Wed");
$soccerPlayers->set("yearOfBirth", 1997);
$soccerPlayers->set("emailContact", "a.wed@email.io");
$soccerPlayers->setArray("attributes", ["fast", "good conditioning"]);

try {
    $soccerPlayers->save();
    echo 'New object created with objectId: ' . $soccerPlayers->getObjectId();
} catch (ParseException $ex) {
    echo 'Error: ' . $ex->getMessage();
}
```

.NET

```csharp
ParseObject soccerPlayers = new ParseObject("SoccerPlayers");
soccerPlayers["playerName"] = "A. Wed";
soccerPlayers["yearOfBirth"] = 1997;
soccerPlayers["emailContact"] = "a.wed@email.io";
soccerPlayers["attributes"] = new List<string> { "fast", "good conditioning" };

await soccerPlayers.SaveAsync();
Console.WriteLine("New object created with objectId: " + soccerPlayers.ObjectId);
```

REST API

```curl
curl -X POST \
  -H "X-Parse-Application-Id: APPLICATION_ID" \
  -H "X-Parse-REST-API-Key: REST_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "playerName": "A. Wed",
    "yearOfBirth": 1997,
    "emailContact": "a.wed@email.io",
    "attributes": ["fast", "good conditioning"]
  }' \
  https://parseapi.back4app.com/classes/SoccerPlayers
```
:::

运行此代码后，您可以在 **数据库** 部分的 Back4app 控制面板中验证新对象。请注意，您不需要手动创建 SoccerPlayers 类；它将在第一次保存对象时自动创建。

![](https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/KuqRY-K2J4cJ0sP4doJuA_screenshot-2024-11-13-at-161114.png)

## 2 - 读取解析对象

要检索保存的数据，您可以使用一个 `ParseQuery`。例如，要通过其 `objectId`来获取上面创建的玩家：

:::CodeblockTabs
JS

```javascript
async function retrievePlayer() {
  const query = new Parse.Query("SoccerPlayers");
  
  try {
    const player = await query.get("HMcTr9rD3s");  // Replace with the actual objectId
    console.log("Player Name: " + player.get("playerName"));
    console.log("Year of Birth: " + player.get("yearOfBirth"));
    console.log("Email Contact: " + player.get("emailContact"));
  } catch (error) {
    console.error("Error retrieving object: " + error.message);
  }
}
```

Flutter

```dart
ParseResponse response = await ParseObject("SoccerPlayers").getObject("HMcTr9rD3s");  // Replace with the actual objectId

if (response.success) {
  ParseObject player = response.result;
  print("Player Name: ${player.get<String>('playerName')}");
  print("Year of Birth: ${player.get<int>('yearOfBirth')}");
  print("Email Contact: ${player.get<String>('emailContact')}");
} else {
  print("Error retrieving object: ${response.error.message}");
}
```

Android

```java
ParseQuery<ParseObject> query = ParseQuery.getQuery("SoccerPlayers");
query.getInBackground("HMcTr9rD3s", (player, e) -> {  // Replace with the actual objectId
  if (e == null) {
    Log.d("Parse", "Player Name: " + player.getString("playerName"));
    Log.d("Parse", "Year of Birth: " + player.getInt("yearOfBirth"));
    Log.d("Parse", "Email Contact: " + player.getString("emailContact"));
  } else {
    Log.e("ParseError", "Error retrieving object: " + e.getMessage());
  }
});
```

iOS

```swift
let query = ParseQuery(className: "SoccerPlayers")
query.get(objectId: "HMcTr9rD3s") { result in  // Replace with the actual objectId
    switch result {
    case .success(let player):
        print("Player Name: \(player["playerName"] ?? "No name")")
        print("Year of Birth: \(player["yearOfBirth"] ?? "No birth year")")
        print("Email Contact: \(player["emailContact"] ?? "No email")")
    case .failure(let error):
        print("Error retrieving object: \(error.localizedDescription)")
    }
}

```

PHP

```php
$query = new ParseQuery("SoccerPlayers");
try {
    $player = $query->get("HMcTr9rD3s");  // Replace with the actual objectId
    echo "Player Name: " . $player->get("playerName") . "\n";
    echo "Year of Birth: " . $player->get("yearOfBirth") . "\n";
    echo "Email Contact: " . $player->get("emailContact") . "\n";
} catch (ParseException $ex) {
    echo 'Error retrieving object: ' . $ex->getMessage();
}
```

.NET

```csharp
var query = ParseObject.GetQuery("SoccerPlayers");
var player = await query.GetAsync("HMcTr9rD3s");  // Replace with the actual objectId

Console.WriteLine("Player Name: " + player.Get<string>("playerName"));
Console.WriteLine("Year of Birth: " + player.Get<int>("yearOfBirth"));
Console.WriteLine("Email Contact: " + player.Get<string>("emailContact"));
```

REST API

```curl
curl -X GET \
  -H "X-Parse-Application-Id: APPLICATION_ID" \
  -H "X-Parse-REST-API-Key: REST_API_KEY" \
  https://parseapi.back4app.com/classes/SoccerPlayers/HMcTr9rD3s  # Replace with the actual objectId
```
:::

除了 `objectId`, 你还可以通过其他参数进行查询（例如，`yearOfBirth`, `playerName`），提供更大的数据搜索灵活性。

## 3 - 更新 Parse 对象

要更新一个对象，首先检索它，为所需属性设置新值，然后调用 `save()` 方法。

:::CodeblockTabs
```javascript
async function updatePlayer() {
  const query = new Parse.Query("SoccerPlayers");
  
  try {
    const player = await query.get("HMcTr9rD3s");  // Replace with the actual objectId
    player.set("yearOfBirth", 1998);
    await player.save();
    console.log("Object updated successfully!");
  } catch (error) {
    console.error("Error updating object: " + error.message);
  }
}
```

Flutter

```dart
ParseObject player = ParseObject("SoccerPlayers")..objectId = "HMcTr9rD3s";  // Replace with the actual objectId
player.set("yearOfBirth", 1998);

ParseResponse response = await player.save();
if (response.success) {
  print("Object updated successfully!");
} else {
  print("Error updating object: ${response.error.message}");
}

```

Android

```java
ParseQuery<ParseObject> query = ParseQuery.getQuery("SoccerPlayers");
query.getInBackground("HMcTr9rD3s", (player, e) -> {  // Replace with the actual objectId
  if (e == null) {
    player.put("yearOfBirth", 1998);
    player.saveInBackground(e1 -> {
      if (e1 == null) {
        Log.d("Parse", "Object updated successfully!");
      } else {
        Log.e("ParseError", "Error updating object: " + e1.getMessage());
      }
    });
  } else {
    Log.e("ParseError", "Error retrieving object: " + e.getMessage());
  }
});
```

iOS

```swift
let query = ParseQuery(className: "SoccerPlayers")
query.get(objectId: "HMcTr9rD3s") { result in  // Replace with the actual objectId
    switch result {
    case .success(var player):
        player["yearOfBirth"] = 1998
        player.save { saveResult in
            switch saveResult {
            case .success:
                print("Object updated successfully!")
            case .failure(let error):
                print("Error updating object: \(error.localizedDescription)")
            }
        }
    case .failure(let error):
        print("Error retrieving object: \(error.localizedDescription)")
    }
}
```

```php
$query = new ParseQuery("SoccerPlayers");
try {
    $player = $query->get("HMcTr9rD3s");  // Replace with the actual objectId
    $player->set("yearOfBirth", 1998);
    $player->save();
    echo "Object updated successfully!";
} catch (ParseException $ex) {
    echo 'Error updating object: ' . $ex->getMessage();
}
```

.NET

```csharp
var query = ParseObject.GetQuery("SoccerPlayers");
var player = await query.GetAsync("HMcTr9rD3s");  // Replace with the actual objectId

player["yearOfBirth"] = 1998;
await player.SaveAsync();
Console.WriteLine("Object updated successfully!");
```

REST API

```curl
curl -X PUT \
  -H "X-Parse-Application-Id: APPLICATION_ID" \
  -H "X-Parse-REST-API-Key: REST_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"yearOfBirth": 1998}' \
  https://parseapi.back4app.com/classes/SoccerPlayers/HMcTr9rD3s  # Replace with the actual objectId
```
:::

## 4 - 删除 Parse 对象

要删除一个对象，请通过 `objectId` 检索它，并使用 `destroy()` 方法.

:::CodeblockTabs
```javascript
async function deletePlayer() {
  const query = new Parse.Query("SoccerPlayers");
  
  try {
    const player = await query.get("HMcTr9rD3s");  // Replace with the actual objectId
    await player.destroy();
    console.log("Object deleted successfully!");
  } catch (error) {
    console.error("Error deleting object: " + error.message);
  }
}
```

Flutter

```dart
ParseObject player = ParseObject("SoccerPlayers")..objectId = "HMcTr9rD3s";  // Replace with the actual objectId

ParseResponse response = await player.delete();
if (response.success) {
  print("Object deleted successfully!");
} else {
  print("Error deleting object: ${response.error.message}");
}
```

Android

```java
ParseQuery<ParseObject> query = ParseQuery.getQuery("SoccerPlayers");
query.getInBackground("HMcTr9rD3s", (player, e) -> {  // Replace with the actual objectId
  if (e == null) {
    player.deleteInBackground(e1 -> {
      if (e1 == null) {
        Log.d("Parse", "Object deleted successfully!");
      } else {
        Log.e("ParseError", "Error deleting object: " + e1.getMessage());
      }
    });
  } else {
    Log.e("ParseError", "Error retrieving object: " + e.getMessage());
  }
});
```

iOS

```swift
let query = ParseQuery(className: "SoccerPlayers")
query.get(objectId: "HMcTr9rD3s") { result in  // Replace with the actual objectId
    switch result {
    case .success(let player):
        player.delete { deleteResult in
            switch deleteResult {
            case .success:
                print("Object deleted successfully!")
            case .failure(let error):
                print("Error deleting object: \(error.localizedDescription)")
            }
        }
    case .failure(let error):
        print("Error retrieving object: \(error.localizedDescription)")
    }
}
```

PHP

```php
$query = new ParseQuery("SoccerPlayers");
try {
    $player = $query->get("HMcTr9rD3s");  // Replace with the actual objectId
    $player->destroy();
    echo "Object deleted successfully!";
} catch (ParseException $ex) {
    echo 'Error deleting object: ' . $ex->getMessage();
}
```

.NET

```csharp
var query = ParseObject.GetQuery("SoccerPlayers");
var player = await query.GetAsync("HMcTr9rD3s");  // Replace with the actual objectId

await player.DeleteAsync();
Console.WriteLine("Object deleted successfully!");
```

REST API

```curl
curl -X DELETE \
  -H "X-Parse-Application-Id: APPLICATION_ID" \
  -H "X-Parse-REST-API-Key: REST_API_KEY" \
  https://parseapi.back4app.com/classes/SoccerPlayers/HMcTr9rD3s  # Replace with the actual objectId
```
:::

:::hint{type="info"}
再次强调，您不必通过其 <font color="#2166ae">`objectId`</font> 来检索对象。Parse 有许多搜索替代方案来从 <font color="#2166ae">`ParseObjects`</font> 中检索信息，您可以在每种不同技术的官方 Parse 文档中找到更多信息。
:::

## 最佳实践和额外提示

- **命名约定**: 使用 ClassNamesLikeThis 来命名类，使用 keyNamesLikeThis 来命名键，以保持代码的组织性和可读性。
- **常见错误检查**: 如果您在连接 Parse SDK 时遇到问题，请验证您的 [SDK 安装和配置](https://www.back4app.com/docs/get-started/parse-sdk).
- **自动字段**: 请记住，每个 Parse 对象自动包含 `createdAt`, `updatedAt`, 和 `objectId` 字段。

## 下一步

在 Back4app 上持久保存和读取您的第一条数据后，我们建议继续使用以下指南探索数据存储。您将找到如何存储支持的数据类型、保存和查询关系数据、使用地理点以及创建优化的数据模型。

::::LinkArray
:::LinkArrayItem{headerType="IMAGE" headerImage="https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/pEkmfq5PdkxC3lmfRzYsE_1.png"}
&#x20;       **[反应原生](https://www.back4app.com/docs/react-native/parse-sdk/react-native-sdk)**
:::

:::LinkArrayItem{headerType="IMAGE" headerImage="https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/tPONkoW1aPPhiAdTvbvrx_sem-nome-rectangle-sticker-landscape.png"}
**[Flutter](https://www.back4app.com/docs/flutter/parse-sdk/parse-flutter-sdk)**
:::

:::LinkArrayItem{headerType="IMAGE" headerImage="https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/vqJJw7ljIhPJ1Yfz7mD9n_3.png"}
[安卓 ](https://www.back4app.com/docs/android/android-project-with-source-code-download)
:::

:::LinkArrayItem{headerType="IMAGE" headerImage="https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/rzkB1YU-Feimt_SWfZUuC_4.png"}
[iOS](https://www.back4app.com/docs/ios/ios-app-template)
:::

:::LinkArrayItem{headerType="IMAGE" headerImage="https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/GsQE6ru-jj2rRbUt7P3Tr_5.png"}
**[JavaScript](https://www.back4app.com/docs/javascript/parse-javascript-sdk)**
:::

:::LinkArrayItem{headerType="IMAGE" headerImage="https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/35IqTes9QhdmijlReYBYZ_6.png"}
[图形查询语言](https://www.back4app.com/docs/parse-graphql/graphql-getting-started)
:::

:::LinkArrayItem{headerType="IMAGE" headerImage="https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/CS13bUltyBMZaO7SPfWC0_1.png"}
[ReactJS](https://www.back4app.com/docs/react/data-objects/react-crud-tutorial)
:::
::::

## 结论

本指南为在 Back4app 上处理数据提供了一个坚实的起点，使得使用 Parse SDK 在各个平台上进行数据存储和操作变得简单。如有任何问题，请随时联系 [Back4app 支持](https://www.back4app.com/support)!