1# 单次I/O任务开发指导 (Promise和async/await) 2 3 4Promise和async/await提供异步并发能力，适用于单次I/O任务的场景开发，本文以使用异步进行单次文件写入为例来提供指导。 5 6 71. 实现单次I/O任务逻辑。 8 9 ```ts 10 import fs from '@ohos.file.fs'; 11 import { BusinessError } from '@ohos.base'; 12 import common from '@ohos.app.ability.common'; 13 14 async function write(data: string, file: fs.File): Promise<void> { 15 fs.write(file.fd, data).then((writeLen: number) => { 16 console.info('write data length is: ' + writeLen) 17 }).catch((err: BusinessError) => { 18 console.error(`Failed to write data. Code is ${err.code}, message is ${err.message}`); 19 }) 20 } 21 ``` 222. 采用异步能力调用单次I/O任务。示例中的filePath的获取方式请参见[获取应用文件路径](../application-models/application-context-stage.md#获取应用文件路径)。 23 24 ```ts 25 async function testFunc(): Promise<void> { 26 let context = getContext() as common.UIAbilityContext; 27 let filePath: string = context.filesDir + "/test.txt"; // 应用文件路径 28 let file: fs.File = await fs.open(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE); 29 write('Hello World!', file).then(() => { 30 console.info('Succeeded in writing data.'); 31 fs.close(file); 32 }).catch((err: BusinessError) => { 33 console.error(`Failed to write data. Code is ${err.code}, message is ${err.message}`); 34 fs.close(file); 35 }) 36 } 37 testFunc(); 38 ``` 39