hunt.sql.visitor.functions.Concat source code

1 /*
2  * Copyright 2015-2018 HuntLabs.cn
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 module hunt.sql.visitor.functions.Concat;
17 
18 // import hunt.sql.visitor.SQLEvalVisitor.EVAL_VALUE;
19 
20 import hunt.sql.ast.SQLExpr;
21 import hunt.sql.ast.expr.SQLMethodInvokeExpr;
22 import hunt.sql.visitor.SQLEvalVisitor;
23 import hunt.sql.visitor.functions.Function;
24 //import hunt.lang;
25 import hunt.String;
26 import hunt.String;
27 import hunt.collection;
28 import hunt.text;
29 
30 import std.concurrency : initOnce;
31 
32 public class Concat : Function {
33 
34     static Concat instance() {
35         __gshared Concat inst;
36         return initOnce!inst(new Concat());
37     }    
38 
39     // public  static Concat instance;
40 
41     // static this()
42     // {
43     //     instance = new Concat();
44     // }
45 
46     public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
47         StringBuilder buf = new StringBuilder();
48 
49         foreach(SQLExpr item ; x.getParameters()) {
50             item.accept(visitor);
51 
52             Object itemValue = item.getAttributes().get(SQLEvalVisitor.EVAL_VALUE);
53             if (itemValue is null) {
54                 return null;
55             }
56             buf.append(itemValue.toString());
57         }
58 
59         return new String(buf.toString());
60     }
61 }