單次I/O任務(wù)開發(fā)指導(dǎo)

Promise和async/await提供異步并發(fā)能力，適用于單次I/O任務(wù)的場景開發(fā)，本文以使用異步進(jìn)行單次文件寫入為例來提供指導(dǎo)。

1. 實(shí)現(xiàn)單次I/O任務(wù)邏輯。

   import fs from '@ohos.file.fs';
   import common from '@ohos.app.ability.common';
   
   async function write(data: string, file: fs.File): Promise<void> {
     fs.write(file.fd, data).then((writeLen: number) => {
       console.info('write data length is: ' + writeLen)
     }).catch((err) => {
       console.error(`Failed to write data. Code is ${err.code}, message is ${err.message}`);
     })
   }

2. 采用異步能力調(diào)用單次I/O任務(wù)。示例中的filePath的獲取方式請參見獲取應(yīng)用文件路徑。

   async function testFunc(): Promise<void> {
     let context = getContext() as common.UIAbilityContext;
     let filePath: string = context.filesDir + "/test.txt"; // 應(yīng)用文件路徑
     let file: fs.File = await fs.open(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
     write('Hello World!', file).then(() => {
       console.info('Succeeded in writing data.');
     }).catch((err) => {
       console.error(`Failed to write data. Code is ${err.code}, message is ${err.message}`);
     })
     fs.close(file);
   }
   testFunc();