Violations NPM

Violations

description

get violated arguments for validation and assertion. this helps design by contract principle for publish API.

Usage

1, write your function, and decide a parameter type.

/**
 * @param {string} name
 * @param {number} age
 */
function login(name, age) {
  // logic
}

2, write a rule for parameter, and create validator.

let Violate = require('violations').Violate;

let rule = {
  name: (val) => {
    if (val === undefined) {
      return 'name is required';
    }
  },
  age: (val) => {
    if (val === undefined) {
      return 'age is required';
    }

    if (val < 0) {
      return 'name should larger than 0';
    }
  }
}

let validator = new Violate(rule);

3, assert parameter before logic, for avoid programmer error.

/**
 * @param {string} name
 * @param {number} age
 */
function login(name, age) {
  validator.assert({ name: name, age: age });

  // logic
}

4, allow user to use validator before calling function.

function main() {
  let name = input.params.name;
  let age = input.params.age;


  let violations = validator.validate({ name: name, age: age });
  if (violations) {
    violations.forEach((message) => {
      user.feedback(message);
    });

    return;
  }

  login(name, age);
}

if validator.assert() failed, it throws AssertionError.

API

paramter

paramter for rules passed 3 args.

val: value of param
name: name of param
_: utility function

let rule = {
  param: (val, name, _) => {
    if (_.isUndefined(value)) {
      return `${name} is required`;
    }
  }
}

return errors

return single errors

let rule = {
  param: (val, name, _) => {
    if (_.isUndefined(value)) {
      return `${name} is required`;
    }
  }
}

let violations = (new Violate(rule)).validate({ param: undefined });
cosnole.log(violations); // [ 'param is required' ]

return multiple errors

let rule = {
  param: (val, name, _) => {
    let messages = [];
    if (value.length < 10) {
      messages.push(`${name} should longer than 10`);
    }

    if (value.match(/[0-9]*/)) {
      messages.push(`${name} should contain number`);
    }
  }
}

let violations = (new Violate(rule)).validate({ param: 'aaa' });
cosnole.log(violations); // [ 'param should longer than 10', 'param should contain number' ]

no errors

let rule = {
  param: (val, name, _) => {
    if (_.isUndefined(value)) {
      return `${name} is required`;
    }
  }
}

let violations = (new Violate(rule)).validate({ param: 'a' });
cosnole.log(violations); // undefined

optional parameter

if parameter is optional, write rule like this.

let rule = {
  param: (val, name, _) => {
    if (_.isUndefined(value)) {
      return; // optional
    }
  }
}

nested rules

if object was nested, write rule like this.

let target = {
  a: 'a',
  b: {
    c: 'c',
    d: 'd'
  }
};

let rules = {
  a: (v) => {
    if (v !== 'a') return 'a should "a"';
  },
  b: {
    // nested
    c: (v) => {
      if (v !== 'c') return 'c should "c"';
    },
    d: (v) => {
      if (v !== 'd') return 'd should "d"';
    }
  }
}