GoJS是一款功能強大，快速且輕量級的流程圖控件，可幫助你在JavaScript 和HTML5 Canvas程序中創建流程圖，且極大地簡化您的JavaScript / Canvas 程序。

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常規鏈接驗證

在某些情況下，您的應用程序的語義將導致有效鏈接目標集以某種方式取決于節點數據（即，鏈接從其開始的節點和端口以及可能的目標節點/端口）只能使用代碼來實現：謂詞函數。

您可以通過設置LinkingBaseTool.linkValidation或Node.linkValidation來實現此類特定于域的驗證。這些謂詞（如果提供）將為鏈接工具考慮的每對端口調用。如果謂詞返回false，則可能無法建立鏈接。在LinkingTool或RelinkingTool上設置屬性會使謂詞應用于所有鏈接操作，而在Node上設置屬性僅適用于涉及該節點的鏈接操作。根據上述屬性，只有在所有標準鏈接檢查均通過的情況下，才調用謂詞。

在此示例中，存在三種不同顏色的節點。該LinkingTool和RelinkingTool自定義為使用的功能，sameColor以確保鏈接只有相同顏色的連接節點。鼠標向下拖動并在橢圓上拖動（光標變為“指針”），開始繪制新鏈接。您將看到，唯一允許的鏈接目標是相同顏色的節點，這些節點尚未從同一節點進行鏈接。

  diagram.nodeTemplate =
    $(go.Node, "Auto",
      $(go.Shape, "Ellipse",
        { cursor: "pointer", portId: "",
          fromLinkable: true, toLinkable: true },
        new go.Binding("fill", "color")),
      $(go.TextBlock,
        { stroke: "white", margin: 3 },
        new go.Binding("text", "key"))
    );

  diagram.linkTemplate =
    $(go.Link,
      { curve: go.Link.Bezier, relinkableFrom: true, relinkableTo: true },
      $(go.Shape, { strokeWidth: 2 },
        new go.Binding("stroke", "fromNode", function(n) { return n.data.color; })
            .ofObject()),
      $(go.Shape, { toArrow: "Standard", stroke: null},
        new go.Binding("fill", "fromNode", function(n) { return n.data.color; })
            .ofObject())
    );

  // this predicate is true if both nodes have the same color
  function sameColor(fromnode, fromport, tonode, toport) {
    return fromnode.data.color === tonode.data.color;
    // this could look at the fromport.fill and toport.fill instead,
    // assuming that the ports are Shapes, which they are because portID was set on them,
    // and that there is a data Binding on the Shape.fill
  }

  // only allow new links between ports of the same color
  diagram.toolManager.linkingTool.linkValidation = sameColor;

  // only allow reconnecting an existing link to a port of the same color
  diagram.toolManager.relinkingTool.linkValidation = sameColor;

  var nodeDataArray = [
    { key: "Red1", color: "red" },
    { key: "Blue1", color: "blue" },
    { key: "Green1", color: "green" },
    { key: "Green2", color: "green" },
    { key: "Red2", color: "red" },
    { key: "Blue2", color: "blue" },
    { key: "Red3", color: "red" },
    { key: "Green3", color: "green" },
    { key: "Blue3", color: "blue" }
  ];
  var linkDataArray = [
    // initially no links
  ];
  diagram.model = new go.GraphLinksModel(nodeDataArray, linkDataArray);

為了強調顏色限制，鏈接的顏色綁定到“ from”節點數據。

限制與節點連接的鏈接總數

可以通過設置GraphObject.toMaxLinks來限制進入端口的鏈接數。同樣，可以通過設置GraphObject.fromMaxLinks來限制從端口出來的鏈接數。但是，如果要限制與端口連接的鏈接總數，而不管它們是進入端口還是離開端口，該怎么辦？這樣的約束只能通過鏈接驗證謂詞來實現。

當要限制任一方向上與每個端口連接的鏈路總數時，可以使用此Node.linkValidation謂詞：

$(go.Node, . . .,
    {
      linkValidation: function(fromnode, fromport, tonode, toport) {
        // total number of links connecting with a port is limited to 1:
        return fromnode.findLinksConnected(fromport.portId).count +
               tonode.findLinksConnected(toport.portId).count < 1; } }, . . .

  $(go.Node, . . .,
    {
      linkValidation: function(fromnode, fromport, tonode, toport) {
        // total number of links connecting with all ports of a node is limited to 1:
        return fromnode.linksConnected.count + tonode.linksConnected.count < 1; } }, . . .

分組驗證

當要限制用戶可以添加到特定組的節點的類型時，可以將謂詞實現為CommandHandler.memberValidation或Group.memberValidation屬性。在CommandHandler上設置屬性會使謂詞應用于所有組，而在Group上設置屬性僅適用于該組。

在此示例中，samePrefix謂詞用于確定是否可以將節點放入組中。嘗試將左側的簡單文本節點拖到右側的任一組中。僅當將節點放到高亮“綠色”的組上時，該節點才被添加為該組的成員。您可以通過移動組以查看文本節點是否也移動來進行驗證。

  // this predicate is true if both node data keys start with the same letter
  function samePrefix(group, node) {
    if (group === null) return true;  // when maybe dropping a node in the background
    if (node instanceof go.Group) return false;  // don't add Groups to Groups
    return group.data.key.charAt(0) === node.data.key.charAt(0);
  };

  diagram.nodeTemplate =
    $(go.Node,
      new go.Binding("location", "loc", go.Point.parse),
      $(go.TextBlock,
        new go.Binding("text", "key"))
    );

  diagram.groupTemplate =
    $(go.Group, "Vertical",
      {
        // only allow those simple nodes that have the same data key prefix:
        memberValidation: samePrefix,
        // don't need to define handlers on member Nodes and Links
        handlesDragDropForMembers: true,
        // support highlighting of Groups when allowing a drop to add a member
        mouseDragEnter: function(e, grp, prev) {
          // this will call samePrefix; it is true if any node has the same key prefix
          if (grp.canAddMembers(grp.diagram.selection)) {
            var shape = grp.findObject("SHAPE");
            if (shape) shape.fill = "green";
            grp.diagram.currentCursor = "";
          } else {
            grp.diagram.currentCursor = "not-allowed";
          }
        },
        mouseDragLeave: function(e, grp, next) {
          var shape = grp.findObject("SHAPE");
          if (shape) shape.fill = "rgba(128,128,128,0.33)";
          grp.diagram.currentCursor = "";
        },
        // actually add permitted new members when a drop occurs
        mouseDrop: function(e, grp) {
          if (grp.canAddMembers(grp.diagram.selection)) {
            // this will only add nodes with the same key prefix
            grp.addMembers(grp.diagram.selection, true);
          } else {  // and otherwise cancel the drop
            grp.diagram.currentTool.doCancel();
          }
        }
      },
      // make sure all Groups are behind all regular Nodes
      { layerName: "Background" },
      new go.Binding("location", "loc", go.Point.parse),
      $(go.TextBlock,
        { alignment: go.Spot.Left, font: "Bold 12pt Sans-Serif" },
        new go.Binding("text", "key")),
      $(go.Shape,
        { name: "SHAPE", width: 100, height: 100,
          fill: "rgba(128,128,128,0.33)" })
    );

  diagram.mouseDrop = function(e) {
    // dropping in diagram background removes nodes from any group
    diagram.commandHandler.addTopLevelParts(diagram.selection, true);
  };

  var nodeDataArray = [
    { key: "A group", isGroup: true, loc: "100 10" },
    { key: "B group", isGroup: true, loc: "100 140" },
    { key: "A1", loc: "10 30" },  // can be added to "A" group
    { key: "A2", loc: "10 60" },
    { key: "B1", loc: "10 90" },  // can be added to "B" group
    { key: "B2", loc: "10 120" },
    { key: "C1", loc: "10 150" }  // cannot be added to either group
  ];
  diagram.model = new go.GraphLinksModel(nodeDataArray, []);

這些組是固定大小的組-它們不使用Placeholder。因此，當將節點放入其中時，該組不會自動調整自身大小以包圍其成員節點。但這在將節點拖出組時也是有好處的。

拖動已經是組成員的節點時，也會調用驗證謂詞。您可以看到將節點放入其現有的包含組是如何可接受的。當將其拖動到組的外部到圖的背景中時，謂詞將以null作為“組”參數被調用。

在此示例中，將節點放到圖的背景中而不是放到一個組中總是可以的。如果要禁止在后臺拖放，可以myDiagram.currentTool.doCancel() 在Diagram.mouseDrop事件處理程序中調用。如果要在后臺拖動過程中顯示反饋，則可以實現一個set 的Diagram.mouseDragOver事件處理程序 myDiagram.currentCursor = "not-allowed"。當在“組”中拖動時，此行為將類似于上面實現的行為。

文字編輯驗證

 您還可以限制用戶在對TextBlock進行就地文本編輯時輸入的文本。首先，要完全啟用任何編輯，您需要將TextBlock.editable設置為true。零件中可能有許多TextBlock，但是您可能希望將文本編輯限制為特定的TextBlock。

通常，用戶可以輸入什么文字沒有限制。如果要提供斷言以在用戶完成編輯時批準輸入，請設置TextEditingTool.textValidation或TextBlock.textValidation屬性。在TextEditingTool上設置屬性會使謂詞應用于所有TextBlock，而在TextBlock上設置屬性僅應用于該文本對象。

  // this predicate is true if the new string has at least three characters
  // and has a vowel in it
  function okName(textblock, oldstr, newstr) {
    return newstr.length >= 3 && /[aeiouy]/i.test(newstr);
  };

  diagram.nodeTemplate =
    $(go.Node, "Auto",
      $(go.Shape, { fill: "lightyellow" }),
      $(go.Panel, "Vertical",
        { margin: 3 },
        $(go.TextBlock,
          { editable: true },  // no validation predicate
          new go.Binding("text", "text1")),
        $(go.TextBlock,
          { editable: true,
            isMultiline: false,  // don't allow embedded newlines
            textValidation: okName },  // new string must be an OK name
          new go.Binding("text", "text2"))
      )
    );

  var nodeDataArray = [
    { key: 1, text1: "Hello", text2: "Dolly!" },
    { key: 2, text1: "Goodbye", text2: "Mr. Chips" }
  ];
  diagram.model = new go.GraphLinksModel(nodeDataArray, []);

請注意，如何編輯頂部的TextBlock如何接受不帶任何元音的文本，但是底部的TextBlock不接受它，而是使文本編輯器處于打開狀態。

如果要在文本編輯完成后執行代碼，請通過調用Diagram.addDiagramListener來實現“ TextEdited” DiagramEvent偵聽器。

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