自定义模式类型

创建基本自定义模式类型

Mongoose 4.4.0 中的新功能：Mongoose 支持自定义类型。但是，在使用自定义类型之前，请了解自定义类型对于大多数用例来说过于复杂。您可以使用 自定义 getter/setter、虚拟属性 和 单个嵌入式文档 来完成大多数基本任务。

让我们来看一个基本模式类型的示例：一个 1 字节的整数。要创建新的模式类型，您需要从 mongoose.SchemaType 继承并向 mongoose.Schema.Types 添加相应的属性。您需要实现的唯一方法是 cast() 方法。

class Int8 extends mongoose.SchemaType {
  constructor(key, options) {
    super(key, options, 'Int8');
  }

  // `cast()` takes a parameter that can be anything. You need to
  // validate the provided `val` and throw a `CastError` if you
  // can't convert it.
  cast(val) {
    let _val = Number(val);
    if (isNaN(_val)) {
      throw new Error('Int8: ' + val + ' is not a number');
    }
    _val = Math.round(_val);
    if (_val < -0x80 || _val > 0x7F) {
      throw new Error('Int8: ' + val +
        ' is outside of the range of valid 8-bit ints');
    }
    return _val;
  }
}

// Don't forget to add `Int8` to the type registry
mongoose.Schema.Types.Int8 = Int8;

const testSchema = new Schema({ test: Int8 });
const Test = mongoose.model('CustomTypeExample', testSchema);

const t = new Test();
t.test = 'abc';
assert.ok(t.validateSync());
assert.equal(t.validateSync().errors['test'].name, 'CastError');
assert.equal(t.validateSync().errors['test'].message,
  'Cast to Int8 failed for value "abc" (type string) at path "test"');
assert.equal(t.validateSync().errors['test'].reason.message,
  'Int8: abc is not a number');