When overriding a method, we may want to add a new formal argument. This may be the case for constructors. If the signature is mixing required and optional arguments, things may become difficult, without mentioning class mixins and decorators.<\/p>\n\n\n\n
When you have a strongly designed base class, you can safely override a method in the subclass and choose there whatever signature you want. But if you happen to change the signature in the base class, you must propagate the changes down the hierarchy to update accordingly all the overridden methods’ signatures. This is a change in design that may have big consequences, and as such is prone to bugs.<\/p>\n\n\n\n
TS playground<\/a><\/p>\n\n\n\n Here is a base class<\/p>\n\n\n\n we override When positional arguments are not practical nor efficient, we can make use of key valued arguments. Each method has a unique argument with a well defined type. Here is the previous example revisited.<\/p>\n\n\n\n In order to override the TS playground<\/a><\/p>\n\n\n\n We first define a Then we define a We have more possibilities<\/p>\n\n\n\n When overriding a method, we may want to add a new formal argument. This may be the case for constructors. If the signature is mixing required and optional arguments, things may become difficult, without mentioning class mixins and decorators. When you have a strongly designed base class, you can safely override a method in the … Continuer la lecture de « Overriding a method signature with optional arguments »<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/posts\/134"}],"collection":[{"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/comments?post=134"}],"version-history":[{"count":2,"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/posts\/134\/revisions"}],"predecessor-version":[{"id":137,"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/posts\/134\/revisions\/137"}],"wp:attachment":[{"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/media?parent=134"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/categories?post=134"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/info.edython.eu\/index.php\/wp-json\/wp\/v2\/tags?post=134"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}class Parent {\n test(foo1: string, bar1: string = 'bar1') {\n console.log(foo1, bar1)\n }\n}\nnew Parent().test('foo1')\n<\/code><\/pre>\n\n\n\ntest<\/code> adding both a required and an optional parameter<\/p>\n\n\n\nclass Child extends Parent {\n test(foo1: string, foo2: string, bar1: string = 'bar1', bar2: string = 'bar2') {\n super.test(foo1, bar1)\n console.log(foo2, bar2)\n }\n}\nconst child = new Child()\nchild.test('foo1', 'foo2')\nchild.test('foo1', 'foo2', 'baz1')\nchild.test('foo1', 'foo2', undefined, 'baz2')\n<\/code><\/pre>\n\n\n\nbar1<\/code> is defined twice<\/li>undefined<\/code> in order to specify only the second optional argument.<\/li>Key Valued arguments<\/h2>\n\n\n\n
type test_r = {\n foo1: string\n bar1?: string\n}\nclass Parent {\n test($: test_r) {\n console.log($.foo1, $.bar1 || 'bar1')\n }\n}\nnew Parent().test({\n foo1: 'foo1'\n})\n<\/code><\/pre>\n\n\n\ntest<\/code> method, we start by extending test_r<\/code>.<\/p>\n\n\n\ntype test_r_r = test_r & {\n foo2: string\n bar2?: string\n}\nclass Child extends Parent {\n test($: test_r_r) {\n super.test($)\n console.log($.foo2, $.bar2 || 'bar2')\n }\n}\nconst child = new Child()\nconst foo1 = 'foo1'\nconst foo2 = 'foo2'\nconst bar1 = 'baz1'\nconst bar2 = 'baz2'\nchild.test({foo1, foo2})\nchild.test({foo1, foo2, bar1})\nchild.test({foo1, foo2, bar2})\n<\/code><\/pre>\n\n\n\nClass Mixins<\/h2>\n\n\n\n
User<\/code> class with a key valued unique constructor argument<\/p>\n\n\n\ntype new_r = {\n [$: string]: any\n name: string\n}\nclass User {\n name: string\n constructor($: new_r) {\n this.name = $.name\n }\n}\nconst user = new User({\n name: \"John Doe\"\n})\nconsole.log(user.name)<\/code><\/pre>\n\n\n\nTagged<\/code> mixins function<\/p>\n\n\n\ntype Tagged_r<R> = R & {\n tag: string\n}\nfunction Tagged<\n TBase extends { new(...args: any[]): {} },\n new_R\n>(Base: TBase) {\n return class extends Base {\n tag?: string\n constructor(...args: any[]) {\n const $ = args[0] as Tagged_r<new_R>\n super($)\n this.tag = $.tag\n }\n }\n}\n\/\/ Create a new class by mixing `Tagged` into an anonymous class that we extend\n\/\/ to restrict the constructor signature.\nclass TaggedUser extends Tagged(User) {\n constructor($: Tagged_r<new_r>) {\n super($)\n }\n}\nconst tagged_user = new TaggedUser({\n name: \"Jane Doe\",\n tag: 'janedoe'\n})\nconsole.log(tagged_user.name)\nconsole.log(tagged_user.tag)<\/code><\/pre>\n\n\n\nnew User({\n name: \"Jane Doe\",\n tag: 'janedoe'\n})\nnew User(user)\nnew User(tagged_user)\nnew TaggedUser(tagged_user)<\/code><\/pre>\n\n\n\nnew_r<\/code> accepts any string key to allow more possibilities<\/li>