是的，基于现有字段且不具有初始值的验证方法

Question

我正在尝试将验证添加到字段中

• 定义后运行验证
• 不运行验证字段再次具有初始值

现在，以下示例适用于第一次检查。它检查是否定义了myField，然后使用myValidation测试验证该字段：

// ✓ runs the validation when it's defined
// ✗ does not run the validation the field has the initial value (again)

const myValidation = Yup.string()
  .min(10, 'Should have at least 10 characters')
  .max(20, 'Should have at last 20 characters');

const validationSchema = yup.object({
  myField: yup.string.when(['myField'], {
    is: (myField) => {
      return !!myField
    },
    then: myValidation(),
  },
)}

但是如何将其与检查初始值结合起来？

我在考虑以下方面：

import * as yup from 'yup';

const myValidation = Yup.string()
  .min(10, 'Should have at least 10 characters')
  .max(20, 'Should have at last 20 characters');

yup.addMethod(Yup.string, 'requiredWhen', function() {
  return this.test({
    name: 'requiredWhen',
    exclusive: true,
    message: 'This is required',

    test: function(value) {
      const { context } = this.options;
      const { myField: initialValue } = context;
      if (value !== initialValue) {
        // is this possible?
        // then: myValidation()
      }

      return true;
    }
  })
});

const validationSchema = yup.object({
  myField: yup.string().requiredWhen(),
});

const validate = (values, initialValues) => validationSchema
  .validate(values, { abortEarly: false, context: initialValues })
  .catch(err => {
    throw yupToFormErrors(err);
  });

const MyForm = ({ initialValues }) => (
  <Formik
    initialValues={initialValues}
    validate={(values) => validate(values, initialValues)}
  />
);

但是我不确定如何在addMethod的测试中应用'then'。