Typescript 基于类内替换的扩展方法更改返回值
我有一个类Typescript 基于类内替换的扩展方法更改返回值,typescript,Typescript,我有一个类FileHandler,然后是一个扩展原始类的FileOrNullHandler类 问题是FileOrNullHandler中从FileHandler继承的方法与原始类中编写的返回类型保持一致 export class FileHandler { static async readFileFromFileQuery (fq: FileQuery): Promise<File> { const { path, encoding, flag } = Fi
FileHandler
,然后是一个扩展原始类的FileOrNullHandler
类
问题是FileOrNullHandler
中从FileHandler
继承的方法与原始类中编写的返回类型保持一致
export class FileHandler {
static async readFileFromFileQuery (fq: FileQuery): Promise<File> {
const { path, encoding, flag } = FileQueryHandler.make(fq);
const content = await promisify(fs.readFile)(path, { encoding, flag })
return { path, encoding, flag, content };
}
static async readFile (a: Path | FileQuery, b?: Omit<FileQuery, 'path'>): Promise<File> {
if (typeof a === 'string') a = FileQueryHandler.getFromPath(a, b);
return this.readFileFromFileQuery(a);
}
static async readFiles (a: (Path | FileQuery)[] | Directory, b?: Omit<FileQuery, 'path'>): Promise<File[]> {
if (a instanceof Array) return Promise.all(a.map(p => this.readFile(p, b)));
return this.readFiles(PathHandler.getFromDirectory(a), b);
}
static async readFilesFromDirectory(a: Path | FileQuery, b?: Omit<FileQuery, 'path'>): Promise<File[]> {
const ps = await DirectoryHandler.readDirectory(a);
if (typeof a === 'string') return await (this).readFiles(ps, b);
return await this.readFiles(ps, a);
}
}
export class FileOrNullHandler extends FileHandler {
static async readFileFromFileQuery (fq: FileQuery): Promise<File | null> {
return orNull(() => FileHandler.readFileFromFileQuery(fq));
}
}
导出类文件处理程序{
静态异步readFileFromFileQuery(fq:FileQuery):承诺{
const{path,encoding,flag}=FileQueryHandler.make(fq);
const content=await promisify(fs.readFile)(路径,{encoding,flag})
返回{path,encoding,flag,content};
}
静态异步读取文件(a:Path | FileQuery,b?:省略):承诺{
if(typeof a=='string')a=FileQueryHandler.getFromPath(a,b);
返回此.readFileFromFileQuery(a);
}
静态异步读取文件(a:(路径|文件查询)[]|目录,b?:省略):承诺{
if(数组的instanceof)返回Promise.all(a.map(p=>this.readFile(p,b));
返回此.readFiles(PathHandler.getFromDirectory(a),b);
}
静态异步readFilesFromDirectory(a:Path | FileQuery,b?:省略):承诺{
const ps=await DirectoryHandler.readDirectory(a);
if(typeof a=='string')返回wait(this).readFiles(ps,b);
返回等待此.readFiles(ps,a);
}
}
导出类FileOrNullHandler扩展FileHandler{
静态异步readFileFromFileQuery(fq:FileQuery):承诺{
返回orNull(()=>FileHandler.readFileFromFileQuery(fq));
}
}
我在这里看到了获得正确类型的两个选项之一
此
设置原始方法的相对返回类型。(可能不可能)FileOrNullHandler
中的方法ReturnType
OOP的通用租户是派生类应该能够替换基类。在这种情况下,派生类无法替换基类,因为派生类具有基类的客户端不知道会期望的返回类型(
null
)
那家伙说我们可以接近你想要的
首先,我不会使用只包含静态方法的类,我会创建一个包含实例方法的类,并声明该实例类型的const
,然后将其导出以供人们作为单例使用
其次,我将移动公共基类中的公共功能,readFileFromFileQuery
方法是抽象的,类是泛型的。这允许我们插入一个返回File
的版本,或者一个返回File | null
的版本,而不违反Typescript(和OOP)一致性规则
最终的解决方案是这样的(我填写了一些类型,不确定它们的实际定义是什么,但我添加了代码无错误所需的最低限度的内容):
抽象类\u FileHandlerBase{
摘要readFileFromFileQuery(fq:FileQuery):承诺;
异步读取文件(a:Path | FileQuery,b?:省略):承诺{
if(typeof a=='string')a=FileQueryHandler.getFromPath(a,b);
返回此.readFileFromFileQuery(a);
}
异步读取文件(a:(路径|文件查询)[]|目录,b?:省略):承诺{
if(数组的instanceof)返回Promise.all(a.map(p=>this.readFile(p,b));
返回此.readFiles(PathHandler.getFromDirectory(a),b);
}
异步readFilesFromDirectory(a:Path | FileQuery,b?:省略):承诺{
const ps=await DirectoryHandler.readDirectory(a);
if(typeof a=='string')返回wait(this).readFiles(ps,b);
返回等待此.readFiles(ps,a);
}
}
导出类_FileHandler扩展_FileHandlerBase{
异步readFileFromFileQuery(fq:FileQuery):承诺{
const{path,encoding,flag}=FileQueryHandler.make(fq);
const content=await promisify(fs.readFile)(路径,{encoding,flag})
返回{path,encoding,flag,content};
}
}
export const FileHandler=new_FileHandler();
导出类_FileOrNullHandler扩展_FileHandlerBase{
异步readFileFromFileQuery(fq:FileQuery):承诺{
返回orNull(()=>FileHandler.readFileFromFileQuery(fq));
}
}
export const FileOrNullHandler=new_FileOrNullHandler();
FileHandler.readFileFromFileQuery(null!)//承诺
FileOrNullHandler.readFileFromFileQuery(null!)//承诺
FileHandler.readFiles(null!)//承诺
FileOrNullHandler.readFiles(null!)//承诺
//一些假设
类型路径=字符串;
接口文件查询{
路径:字符串,标志?:字符串,编码?:字符串|空
}
导出接口文件{
路径:字符串,标志?:字符串,编码:字符串|未定义|空,内容:缓冲区|字符串
}
接口目录{
路径:字符串,isDir:true
}
声明var FileQueryHandler:{
make(fq:FileQuery):FileQuery
getFromPath(s:string,b?:省略):FileQuery;
}
声明var DirectoryHandler:{
readDirectory(a:Path | FileQuery):FileQuery[]
}
类型省略=拾取
函数orNull(fn:()=>T){
试一试{
返回fn();
}捕获(e){
返回null;
}
}
声明常量路径处理程序:{
getFromDirectory(d:Directory):FileQuery[];
}
abstract class _FileHandlerBase<T> {
abstract readFileFromFileQuery(fq: FileQuery): Promise<T>;
async readFile(a: Path | FileQuery, b?: Omit<FileQuery, 'path'>): Promise<T> {
if (typeof a === 'string') a = FileQueryHandler.getFromPath(a, b);
return this.readFileFromFileQuery(a);
}
async readFiles(a: (Path | FileQuery)[] | Directory, b?: Omit<FileQuery, 'path'>): Promise<T[]> {
if (a instanceof Array) return Promise.all(a.map(p => this.readFile(p, b)));
return this.readFiles(PathHandler.getFromDirectory(a), b);
}
async readFilesFromDirectory(a: Path | FileQuery, b?: Omit<FileQuery, 'path'>): Promise<T[]> {
const ps = await DirectoryHandler.readDirectory(a);
if (typeof a === 'string') return await (this).readFiles(ps, b);
return await this.readFiles(ps, a);
}
}
export class _FileHandler extends _FileHandlerBase<File> {
async readFileFromFileQuery(fq: FileQuery): Promise<File> {
const { path, encoding, flag } = FileQueryHandler.make(fq);
const content = await promisify(fs.readFile)(path, { encoding, flag })
return { path, encoding, flag, content };
}
}
export const FileHandler = new _FileHandler();
export class _FileOrNullHandler extends _FileHandlerBase<File | null> {
async readFileFromFileQuery(fq: FileQuery): Promise<File | null> {
return orNull(() => FileHandler.readFileFromFileQuery(fq));
}
}
export const FileOrNullHandler = new _FileOrNullHandler();
FileHandler.readFileFromFileQuery(null!) // Promise<File>
FileOrNullHandler.readFileFromFileQuery(null!) // Promise<File | null>
FileHandler.readFiles(null!) // Promise<File[]>
FileOrNullHandler.readFiles(null!) // Promise<(File | null)[]>
// Some assumptions
type Path = string;
interface FileQuery {
path: string, flag?: string, encoding?: string | null
}
export interface File {
path: string, flag?: string, encoding: string | undefined | null, content: Buffer | string
}
interface Directory {
path: string, isDir: true
}
declare var FileQueryHandler: {
make(fq: FileQuery): FileQuery
getFromPath(s: string, b?: Omit<FileQuery, 'path'>): FileQuery;
}
declare var DirectoryHandler : {
readDirectory(a: Path | FileQuery) : FileQuery[]
}
type Omit<T, K> = Pick<T, Exclude<keyof T, K>>
function orNull<T>(fn: () => T) {
try {
return fn();
} catch (e) {
return null;
}
}
declare const PathHandler: {
getFromDirectory(d: Directory): FileQuery[];
}