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\n\n\n- [@alcadica/contract](#alcadicacontract)\n - [Install](#install)\n - [Examples](#examples)\n - [Licence](#licence)\n\n## Install\n\n```bash\nnpm i --save @alcadica/contract\n```\n\nThis package provides a simple but powerful way to estabilish a contract between a datasource and an entity. A contract is used to handle data channeling between a caller (application layer) and an owner (data layer, contract provider).\n\n## Examples\n\n```ts\nimport contract from '@alcadica/contract';\n\nclass MyEntity {\n public foo: string = '';\n}\n\nlet instance = new MyEntity();\n\nlet MyEntityContract = contract.createFromInstance(instance);\n\nMyEntityContract.validators.foo.validate = entity => entity.foo.length > 0;\n\nconsole.log(MyEntityContract.valid) // outputs false\n\ninstance.foo = '123';\n\nconsole.log(MyEntityContract.valid) // outputs true\n\nlet newinstance = new MyEntity();\n\nMyEntityContract.entity = newinstance;\n\nconsole.log(MyEntityContract.valid) // outputs false\n```\n\nCreating a custom validator\n\n```typescript\nimport contract from '@alcadica/contract';\n\nclass Test {\n public constructor (\n public bar: string,\n public foo: number\n ) {};\n}\n\nconst testContract = contract.createFromClass(Test, 'hello', 100);\n\ntestContract.entity.foo.validate = () => {\n return (value: string) => {\n return contract.createValidatorOutput(value.length > 5, 'foo length must be greater than 5');\n }\n}\n```\n\nUsing in express.js for input data validation\n\n```typescript\nimport Contract from '@alcadica/contract';\nimport * as express from 'express';\n\nconst route = express.Route();\nconst contract = Contract.create(['bar', 'foo']);\n\n// we assume that the server will receive a json like this\n// { \"foo\": \"hello world\", \"bar\": 123 }\n\ncontract.validators.bar.validator = (value: number) => value && value > 3 && value < 6;\ncontract.validators.foo.validator = (value: string) => value && value.length > 3;\n\nroute.post('/resource', (request, response) => {\n contract.entity = request.body;\n\n if (contract.valid) {\n response.status(200).json(contract);\n } else {\n response.status(400).json(contract);\n }\n});\n```\n\nUsing react form\n\n```tsx\nimport Contract from '@alcadica/contract';\nimport React from 'react';\n\ninterface IState {\n name: string;\n email: string;\n}\n\nconst getInitialState: () => IState = () => ({\n name: '',\n email: '',\n});\n\nexport default class MyForm extends React.Component<{}, IState> {\n public contract = Contract.createFromInstance(getInitialState());\n public state = getInitialState();\n\n public componentDidMount() {\n this.contract.validators.name.validator = (value: string) => value.length >= 3;\n this.contract.validators.name.validator = (email: string) => /^[^@\\s]+@[^@\\s]+\\.[^@\\s]+$/.test(value);\n }\n\n public createChangeListener(name: keyof IState) {\n return (event: React.ChangeEvent