Typescript 非空断言运算符仍引发编译时错误
我正在使用Typescript 非空断言运算符仍引发编译时错误,typescript,typeorm,Typescript,Typeorm,我正在使用运算符,告诉编译器忽略可能的未定义的值,但它似乎仍会引发错误 let rooms :Room[]; rooms = []; for (let id of roomIds) { let room: Room = await getRepository(Room).findOne({where: {id: id}})!; if(room) rooms.push(room);
运算符,告诉编译器忽略可能的未定义的
值,但它似乎仍会引发错误
let rooms :Room[];
rooms = [];
for (let id of roomIds) {
let room: Room = await getRepository(Room).findOne({where: {id: id}})!;
if(room) rooms.push(room);
}
错误呢
src/resolvers/BookingResolver.ts:65:21 - error TS2322: Type 'Room | undefined' is not assignable to type 'Room'.
Type 'undefined' is not assignable to type 'Room'.
65 let room: Room = await getRepository(Room).findOne({where: {id: id}})!;
~~~~
at createTSError (/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts-node/src/index.ts:513:12)
at reportTSError (/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts-node/src/index.ts:517:19)
at getOutput (/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts-node/src/index.ts:752:36)
at Object.compile (/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts-node/src/index.ts:968:32)
at Module.m._compile (/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts-node/src/index.ts:1056:42)
at Module._extensions..js (internal/modules/cjs/loader.js:1158:10)
at Object.require.extensions.<computed> [as .ts] (/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts-node/src/index.ts:1059:12)
at Module.load (internal/modules/cjs/loader.js:986:32)
at Function.Module._load (internal/modules/cjs/loader.js:879:14)
at Module.require (internal/modules/cjs/loader.js:1026:19)
[nodemon] app crashed - waiting for file changes before starting.
src/resolvers/BookingResolver.ts:65:21-错误TS2322:Type“Room | undefined”不可分配给Type“Room”。
类型“未定义”不可分配给类型“房间”。
65 let room:room=等待getRepository(room).findOne({where:{id:id}})!;
~~~~
在CreateTError(/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts node/src/index.ts:513:12)
在报告错误(/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts node/src/index.ts:517:19)
在getOutput(/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts node/src/index.ts:752:36)
在Object.compile(/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts node/src/index.ts:968:32)
在Module.m._compile(/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts node/src/index.ts:1056:42)
at Module._extensions..js(internal/modules/cjs/loader.js:1158:10)
在Object.require.extensions。[as.ts](/home/tes/work/adey/source/AdeyBackEnd/server/node_modules/ts node/src/index.ts:1059:12)
在Module.load(内部/modules/cjs/loader.js:986:32)
at Function.Module._load(内部/modules/cjs/loader.js:879:14)
at Module.require(内部/modules/cjs/loader.js:1026:19)
[nodemon]应用程序崩溃-在启动前等待文件更改。
我假设findOne
返回一个承诺
,在这种情况下,您需要应用代码>运算符到的结果等待
,但现在您正在应用在等待之前执行code>
因此,请将代码更改为以下内容:
const rooms: Room[] = [];
for( let id of roomIds ) {
const room: Room = ( await getRepository(Room).findOne( { where: { id: id } } ) )!;
rooms.push( room );
}
const rooms: Room[] = [];
for( let id of roomIds ) {
const room: Room | undefined = await getRepository(Room).findOne( { where: { id: id } } );
rooms.push( room! );
}
…虽然我个人会这样写:
const rooms: Room[] = [];
for( let id of roomIds ) {
const room: Room = ( await getRepository(Room).findOne( { where: { id: id } } ) )!;
rooms.push( room );
}
const rooms: Room[] = [];
for( let id of roomIds ) {
const room: Room | undefined = await getRepository(Room).findOne( { where: { id: id } } );
rooms.push( room! );
}
…或者更好的做法是,使用单个存储库对象和并行请求,这样程序总体运行速度会快得多:
const roomsRepo = getRepository(Room);
const roomsResults = await Promise.all( roomIds.map( roomId => roomsRepo.findOne( { where: { id: roomId } } ) ) );
const rooms = roomsResults.filter( r => r ); // Filter out `undefined` values.
你的代码>运算符正在应用于承诺
。您需要移动
到wait
表达式之外。如何定义findOne
呢?感谢这两项工作:)