如何允许null，但禁止undefined？

Question

例如对于数据库行，我们可能需要不能未定义的可空属性：

class DbRow {
  @IsNumber()
  id!: number;

  @IsNumber()
  numNullable!: number | null;
}

所以 numNullable 可以是数字或 null - 但绝不能是 undefined.

我们如何在 class-validator 中表达这个？

添加 @Optional() 不起作用，因为那样也会允许 undefined
我也没有使用自定义验证器

Answer 1

这是库的限制，它不允许条件分支。最好的方法是编写自己的只允许空值的验证器。

Answer 2

事实证明，这可以通过使用 conditional validation ValidateIf:

class DbRow {
  @IsNumber()
  id!: number;

  @IsNumber()
  @ValidateIf((object, value) => value !== null)
  numNullable!: number | null;
}

这是一个stackblitz example

Answer 3

这是我的解决方案：

import { ValidationOptions, ValidateIf } from 'class-validator';
export function IsNullable(validationOptions?: ValidationOptions) {
  return ValidateIf((_object, value) => value !== null, validationOptions);
}

用法

import { plainToClass } from 'class-transformer';
import { IsNumber, validateSync } from 'class-validator';
import { IsNullable } from 'src/common/utils/is-nullable.decorator';
class SampleDto {
  @IsNullable()
  @IsNumber()
  foo: number | null;
}
describe('IsNullable', () => {
  it('should disable other validators when given property is null', () => {
    expect(validateSync(plainToClass(SampleDto, { foo: null }))).toEqual([]);
  });
  it('should allow other validators to work when given property is not null', () => {
    expect(validateSync(plainToClass(SampleDto, { foo: 1 }))).toEqual([]);
    expect(validateSync(plainToClass(SampleDto, { foo: '1' }))[0].constraints.isNumber).toMatch('foo must be a number');
  });
  it('should not allow undefined', () => {
    expect(validateSync(plainToClass(SampleDto, { foo: undefined })).length).toBeGreaterThan(0);
  });
});

Answer 4

这是从 class-validator 导出的 IsOptional 的扩展版本。

import {
  ValidationOptions,
  ValidateIf,
  IsOptional as IsOptionalValidator,
} from 'class-validator';

/**
 * Checks if value is missing and if so, ignores all validators.
 *
 * @param nullable If `true`, all other validators will be skipped even when the value is `null`. `false` by default.
 * @param validationOptions {@link ValidationOptions}
 *
 * @see IsOptional exported from `class-validator.
 */
export function IsOptional(
  nullable = false,
  validationOptions?: ValidationOptions,
) {
  if (nullable) {
    return IsOptionalValidator(validationOptions);
  }

  return ValidateIf((ob: any, v: any) => {
    return v !== undefined;
  }, validationOptions);
}

如何允许null，但禁止undefined？

How to allow null, but forbid undefined?

class-validator