把需要的下一步操作的对象通过上一步操作返回回来。使完成某些功能具有持续性。
代码更精简优雅。链式操作能大大精简代码量,多项操作一行代码一气呵成,搞定;链式操作应用场景除了前端jquery方面的操作dom,后端语言PHP、Go、Python、Java等web框架都有orm的身影.
//goChain.go package main import ( "fmt" ) type link struct { Table string Limit string Where string Field string } func (o *link) setTable(table string) *link { o.Table = table return o } func (o *link) setLimit(limit string) *link { o.Limit = limit return o } func (o *link) setWhere(where string) *link { o.Where = where return o } func (o *link) setField(field string) *link { o.Field = field return o } func (o *link) print() { fmt.Printf("SELECT %s FROM %s WHERE %s LIMIT 0,%d", o.Field, o.Table, o.Where, o.Limit) } func main() { o := link{} o.setTable("user").setField("id, username, password ").setWhere(" id = 1").setLimit("1").print() //输出结果:SELECT id, username, password FROM user WHERE id = 1 LIMIT 0,%!d(string=1) }
2.实现链式操作可以使用PHP的魔术方法_call。但是我这里实现还是愿意一开始说的返回对象本身的思路没有用到_call
<?php //phpChain.php class Link { static public $_garr= array( 'table'=>'', 'limit' =>0, 'where' => ' 1=1 ', 'field' => ' ' ); function __construct($table) { self::$_garr['table'] = $table ; } public function where($where='') { self::$_garr['where'].= ' and '.$where ; return $this; } public function field($field) { self::$_garr['field'] = $field ; return $this; } public function top($top) { self::$_garr['limit'] = $top; return $this; } public function query() { $sql_arr = self::$_garr; $sql = "SELECT {$sql_arr['field']} FROM {$sql_arr['table']} WHERE {$sql_arr['where']} LIMIT 0, {$sql_arr['limit']}"; return $sql; } }; $db = new Link("user"); $sql = $db->top(10) ->field("id, username, password ") ->where(" id = 1") ->query(); print($sql); //结果:SELECT id, username, password FROM user WHERE 1=1 and id = 1 LIMIT 0, 10 ?>
#PythonChain.py class Link: def __init__(self, table): self.table = table def where(self, where): self.where = 'and ' +where return self; def field(self, field): self.field = field return self def top(self, top): self.limit = top return self; def query(self): sql = 'SELECT '+self.field+' FROM '+self.table+' WHERE 1=1 '+ self.where+' limit 0,'+self.limit return sql p = Link('user') sql = p.top(str(10)).field('id, username, password').where('id=1').query() print(sql) #输出结果:SELECT id, username, password FROM user WHERE 1=1 and id=1 limit 0,10
//Link.java public class Link { private String table; private int limit; private String where; private String field; public Link setTable(String table) { this.table = table; return this; } public Link setLimit(int limit) { this.limit = limit; return this; } public Link setWhere(String where) { this.where = where; return this; } public Link setField(String field) { this.field = field; return this; } public void printSql() { //System.out.println(this.address); System.out.println(" SELECT "+this.field+"FROM "+this.table+" WHERE "+this.where+" LIMIT 0,"+this.limit); //return this; } }
Test.java测试代码:
//Test.java public class Test { public static void main(String[] args) { Link link1 = new Link(); link1.setTable("user").setLimit(10).setField(" id, username, password ").setWhere(" id = 1").printSql(); //结果: SELECT id, username, password FROM user WHERE id = 1 LIMIT 0,10 } }
4.Javascript 的链式操作大家最熟悉不过了,jquery 的整个框架就是链式操作实现,我这里写的demo 当然跟jquery 实现的思路不是一致的,jquery具体实现方式可以看jquery源码。
var Link = function (table){ this.sql = { "table" : "", "where" : " 1=1 ", "limit" : 0, "field" : "" } this.sql.table = table; } Link.prototype = { where : function (where) { this.sql.where += " and "+ where; return this; }, field : function (field) { this.sql.field = field; return this; }, top : function (limit) { this.sql.limit = limit; return this; }, query : function () { var sqlstr = "SELECT "+this.sql.field+" FROM "+this.sql.table +" WHERE "+ this.sql.where+ " LIMIT 0,"+this.sql.limit; return sqlstr; } } var db = new Link("user"); var $val = db.where(" id = 1") .top(10) .field(" id, username , password") .query(); console.log($val);
完整版HTML代码:
<!DOCTYPE html> <!-- JsChain.html页面 --> <html> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>JS链式操作</title> <link rel="stylesheet" href=""> </head> <body> <script type="text/javascript"> window.onload=function(){ var Link = function (table){ this.sql = { "table" : "", "where" : " 1=1 ", "limit" : 0, "field" : "" } this.sql.table = table; } Link.prototype = { where : function (where) { this.sql.where += " and "+ where; return this; }, field : function (field) { this.sql.field = field; return this; }, top : function (limit) { this.sql.limit = limit; return this; }, query : function () { var sqlstr = "SELECT "+this.sql.field+" FROM "+this.sql.table +" WHERE "+ this.sql.where+ " LIMIT 0,"+this.sql.limit; return sqlstr; } } var db = new Link("user"); var $val = db.where(" id = 1") .top(10) .field(" id, username , password") .query(); console.log($val); //这里需要打开浏览器控制台 //输出结果: SELECT id, username , password FROM user WHERE 1=1 and id = 1 LIMIT 0,10 } </script> </body> </html>
using System; namespace ConsoleApplication1 { public class sqlHelp { public sqlHelp (string table) { this.table = table; } public string where = ""; public string field = ""; public int limit = 0; public string table = ""; } static class LinkExtended { public static sqlHelp Where(this sqlHelp h, string where) { h.where += " and"+ where; return h; } public static sqlHelp Top(this sqlHelp h, int limit) { h.limit = limit; return h; } public static sqlHelp Field(this sqlHelp h, string field) { h.field = field; return h; } public static string Query(this sqlHelp h) { string sql = string.Format("SELECT {0} FROM {1} WHERE 1=1 {2} LIMIT 0, {3}", h.field, h.table, h.where, h.limit); return sql; } } class Program { static void Main(string[] args) { sqlHelp db = new sqlHelp("user"); string sql = db.Top(10) .Field("id, username, password") .Where(" id =1") .Query(); Console.WriteLine(sql); Console.ReadLine(); } } }
6.asp(vbscript)这个我一直在网上搜索资料也没见有人写过, 我自认为我这里写出来的是全网第一份(当然可能人家有我没找到而已,呵呵所以自我陶醉下),因为vbscript 本身的类是非常弱的,但是也提供了 defalut 和 me 这样好用的特性,所以实现链式也不是什么难事( 如果熟练vbscript 的朋友可以能会想到 with .. end with 语言 其实这个语言本身有点链式的味道,但是思路上不叫链式操作)
Class Link '声明一个全局字典 Dim sqlD public Default function construct(table) Set sqlD = CreateObject("Scripting.Dictionary") Call sqlD.add("table", table) Set construct = me End function Public Function where(whereStr) Call sqlD.add("where", whereStr) Set Where = me End Function Public Function top(limit) Call sqlD.add("limit", limit) Set top = me End Function Public Function field(fieldStr) Call sqlD.add("field", fieldStr) Set field = me End Function Public Function query() Dim sql sql = "SELECT "& sqlD.item("field")&" FROM "&sqlD.item("table")&" WEHRE "&sqlD.item("where") query = sql End function End Class Dim db, sql Set db = (New Link)("user") sql = db.top(10).field("id, username, password").Where(" id = 1").query() msgbox sql