Javascript变量作用域问题-错误:类型错误:this.graphics未定义

我知道这个问题已经解决了，但我仍然不明白。我已经阅读了StackOverFlow自己的"this"关键字解释（以及其中的Mike West文章）以及其他与范围相关的问题。我不知道为什么我不明白，所以我向更精明的JavaScript开发人员寻求帮助。

从代码和注释来看，它应该是不言自明的。但它正在查询ESRI地图服务，返回图形并将其放置在地图上。

但问题出在showResults函数中，我调用this.graphics，这是地图的图形属性（图形层）。我知道它现在超出了范围（我花了比我想承认的更多的时间来弄清楚），但我如何才能把它放回范围，这样我才能使用它？即使我大幅修改了代码。。。

define([
"dojo/_base/declare",
"dojo/on",
"dijit/_WidgetBase",
"dijit/_TemplatedMixin",
"dijit/_WidgetsInTemplateMixin",
"dijit/form/Button",
"dijit/form/Form",
"dijit/form/FilteringSelect",
"dijit/form/ValidationTextBox",
"dojo/_base/array",
"dojo/_base/Color",
"dojo/_base/lang",
"esri/tasks/find",
"dojo/text!./Find/templates/Find.html"
], function(declare, on, _WidgetBase, _TemplatedMixin, _WidgetsInTemplateMixin, Button, Form, FilteringSelect, ValidationTextBox, array, Color, lang, find, FindTemplate) {
//anonymous function to load CSS files required for this module
(function() {
    var css = [require.toUrl("gis/dijit/Find/css/Find.css")];
    var head = document.getElementsByTagName("head").item(0),
        link;
    for(var i = 0, il = css.length; i < il; i++) {
        link = document.createElement("link");
        link.type = "text/css";
        link.rel = "stylesheet";
        link.href = css[i].toString();
        head.appendChild(link);
    }
}());
// Query Dijit
return declare([_WidgetBase, _TemplatedMixin, _WidgetsInTemplateMixin], {
    widgetsInTemplate: true,
    templateString: FindTemplate,
    graphics: null,
    findTask: null,
    findParams: null,
    results: [],
    serverError: null,
    queryLayer: null,
    searchText: null,
    postCreate: function() {
        // Method is used to call a superclass method. It's good practice to assume that you are overriding a method that may 
        // do something important in a class up the inheritance chain
        this.inherited(arguments);
        // Create graphics layer and add it to the map
        this.graphics = new esri.layers.GraphicsLayer({id:"queryGraphics"});
        this.map.addLayer(this.graphics);
        // Create find task with url to map service
        this.findTask = new esri.tasks.FindTask("arcgis/rest/services/MapServer");
        // Create find parameters and define known values
        this.findParams = new esri.tasks.FindParameters();     
        this.findParams.outSpatialReference = this.map.spatialReference;
        this.findParams.returnGeometry = true;
        this.findParams.layerIds = [1];
        this.findParams.searchFields = ["OBJECTID", "Gauge ID", "FV_ID", "FDC_ID", "Flood_Stage", "Flood_Line", "Municipality", "WATERSHED"]; 
        // Listen for Submit button click
        on(this.submitButton, 'click', lang.hitch(this, 'execute'));
    },
    // Submit button click event
    execute: function execute() {   
        // Set the WHERE search text
        this.findParams.searchText = dojo.byId("searchText").value;
        // Sends a request to the ArcGIS REST map service resource to perform a search based 
        // on the FindParameters specified in the findParameters argument. On completion, the 
        // onComplete event is fired and the optional callback function is invoked.
        this.findTask.execute(this.findParams, this.showResults, this.showError); 
    },
    // Fires when the find operation is complete and returns an array of FindResult
    showResults: function showResults(results) {
        this.graphics.clear();
        // Build an array of attribute information and add each found graphic to the map
        dojo.forEach(results, function(result) {
            var symbol;
            switch(result.feature.geometry.type) {
                case "point":
                    symbol = new esri.symbol.SimpleMarkerSymbol(esri.symbol.SimpleMarkerSymbol.STYLE_CIRCLE, 10, new esri.symbol.SimpleLineSymbol(esri.symbol.SimpleLineSymbol.STYLE_SOLID, new Color([255, 0, 0]), 1), new Color([255, 0, 0, 1.0]));
                    break;
                case "polyline":
                    symbol = new esri.symbol.SimpleLineSymbol(esri.symbol.SimpleLineSymbol.STYLE_DASH, new Color([255, 0, 0]), 1);
                    break;
                case "polygon":
                    symbol = new esri.symbol.SimpleFillSymbol(esri.symbol.SimpleFillSymbol.STYLE_SOLID, new esri.symbol.SimpleLineSymbol(esri.symbol.SimpleLineSymbol.STYLE_DASHDOT, new Color([255, 0, 0]), 2), new Color([255, 255, 0, 0.0]));
                    break;
                default:
                    symbol = new esri.symbol.SimpleMarkerSymbol(esri.symbol.SimpleMarkerSymbol.STYLE_CIRCLE, 10, new esri.symbol.SimpleLineSymbol(esri.symbol.SimpleLineSymbol.STYLE_SOLID, new Color([255, 0, 0]), 1), new Color([255, 0, 0, 1.0]));
            }
            var graphic = new esri.Graphic(result.feature.geometry, symbol);
            this.graphics.add(graphic);
        });
    },
    // Fires if the find execution fails to complete
    showError: function showError(serverError) {
        alert("The server encountered an error. Error: " + serverError);
    }
});
});

回答后更新：

所以，解决这个问题的不是一个答案，而是两个答案的结合。我把布法罗对的回答纳入其中

this.findTask.execute(this.findParams, lang.hitch(this, this.showResults), this.showError);

布法罗对克雷格回答的评论

dojo.forEach(results, function(result) {  
...
}, this);

但克雷格的也会在这里工作。再加上泰米尔语的回答，我确信这也会奏效。

所以我会把布法罗的作为答案，但这三本书都值得更多读者阅读。