TypeORM 中的 ColumnTypeUndefinedError

Question

Can someone tell me why, on launch my project i get this error:

ColumnTypeUndefinedError: Column type for Order#author is not defined and cannot be guessed. Make sure you have turned on an "emitDecoratorMetadata": true option in tsconfig.json. Also make sure you have imported "reflect-metadata" on top of the main entry file in your application (before any entity imported).If you are using JavaScript instead of TypeScript you must explicitly provide a column type.

here is my column like above,

    @Column({
        nullable: true
    })
    author: User;

thanks for any help!

Answer 1

It is because the database does not know about User type.

Change User to string and the error will go away, because the database knows about string :

@Column({
        nullable: true
    })
    author: string;

If you want User instead of string , use @ManyToOne instead of @Column. This sets up a foreign key relationship to the User table, and if you add eager: true the User entity will be loaded automatically with the base entity when you use any of the TypeOrm find* methods:

@ManyToOne(() => User, { eager: true })
author: User;

Answer 2

you are getting this error because your tsconfig.json file is not properly configured. add the following to your file.

{
    "emitDecoratorMetadata": true,
    "lib": ["es5", "es6", "dom"],  
    "moduleResolution": "node",
    "target": "es5", 
}

then you have to run

npm run tsc

after you've editted your tsconfig file, for recompilation.