hunt.sql.visitor.functions.Elt 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.Elt;
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.Number;
25 import hunt.String;
26 import hunt.String;
27 import hunt.collection;
28 
29 import std.concurrency : initOnce;
30 
31 public class Elt : Function {
32 
33     static Elt instance() {
34         __gshared Elt inst;
35         return initOnce!inst(new Elt());
36     }    
37 
38     // public  static Elt instance;
39 
40     // static this()
41     // {
42     //     instance = new Elt();
43     // }
44 
45     public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
46         if (x.getParameters().size() <= 1) {
47             return cast(Object)(SQLEvalVisitor.EVAL_ERROR);
48         }
49 
50         SQLExpr param0 = x.getParameters().get(0);
51         param0.accept(visitor);
52 
53         Object param0Value = param0.getAttributes().get(SQLEvalVisitor.EVAL_VALUE);
54         int param0IntValue;
55         if (!(cast(Number)(param0Value) !is null)) {
56             return cast(Object)(SQLEvalVisitor.EVAL_ERROR);
57         }
58         param0IntValue = (cast(Number) param0Value).intValue();
59 
60         if (param0IntValue >= x.getParameters().size()) {
61             return null;
62         }
63 
64         SQLExpr item = x.getParameters().get(param0IntValue);
65         item.accept(visitor);
66 
67         Object itemValue = item.getAttributes().get(SQLEvalVisitor.EVAL_VALUE);
68         return itemValue;
69     }
70 }