Create Custom Enum Type

问题:

I want to create a custom enum type for the custom control like https://sapui5.hana.ondemand.com/docs/api/symbols/sap.ui.core.ValueState.html#.Error.

My questions are:

• How can I create an enum type?
• On the custom control, you will be able only to pass property enum
  type. How can I validate if the given enum is valid or not?

回答1:

In order to create an enum type in UI5, there are certain rules to take into account:

• The enum definition must be a plain object. Internally, it's validated via jQuery.isPlainObject.
• Each key-value pair must be identical to each other.
• Renaming is not supported.
• Only keys and values of type string are supported.

Example:

{   Red: "Red",   Yellow: "Yellow",   Blue: "Blue" }

That being said, in order to actually make use of the enum object:

1. The enum object must be first globally accessible. One way to do this is to define a module that consists of a plain object and making it available under the module name. For example:

   /** * file: PrimaryColor.js * path: "custom/control/type/enum/" * namespace: "demo" */ sap.ui.define({ // module value   Red: "Red",   Yellow: "Yellow",   Blue: "Blue", }, true); // resulting module name: "demo.custom.control.type.enum.PrimaryColor"

2. The module name of the object must be assigned to the type in the property definition:

   sap.ui.define([   "sap/ui/core/Control",   "./MyColorPickerRenderer",   "./type/enum/PrimaryColor", // Defines the module and prevents fetching it via sync XHR ], function(Control) {   "use strict";    return Control.extend("demo.custom.control.ColorPicker", {     metadata: {       properties: {         "selectedColor": {           type: "demo.custom.control.type.enum.PrimaryColor"         }       }     },     // ...   }); });

In my example above, it's the selectedColor property that awaits only "Red", "Yellow", or "Blue". Let's test it:

• new ColorPicker().getMetadata().getProperty("selectedColor").getType().isEnumType() returns true (getType returns the created sap.ui.base.DataType

• new ColorPicker().setSelectedColor("Hans") throws an error as expected:

• new ColorPicker().setSelectedColor("Yellow")

---

Note

Do not try to create an enum type via DataType.create.

Array types and enumeration types cannot be created with this method. They're created on-the-fly by DataType.getType when such a type is looked up. ^[source]

References

• DataType source code (search for "enum" occurances)
• Documentation topic Defining Control Properties

回答2:

Start off by defining your enum...

MessageType.js

sap.ui.define([], function() {     "use strict";      return {       Unread: "Unread",       Read: "Read"     }; });

Next, mark this enum as a dependency in your custom control so that you are able to validate the value.

MyControl.js

    sap.ui.define(["sap/ui/core/Control", "/path/to/MessageType.js"], function(Control, MessageType) {          Control.extend("myControl", {             someMethod: function(sMessageType) {                 // Validate if we are dealing with a valid message type                 var aKeys = Object.keys(MessageType);                 var bValidEnumValue = aKeys.some(function(sKey) {                     if (MessageType[sKey]) {                         return true;                     }                 });                  // Do other stuff..             }         });     });

Of course the way to check if you are dealing with a valid enum value can be implemented in different ways depending on what you're trying to do.

if (sMessageType === MessageType.Read) {    // do something } else if (sMessageType === MessageType.Unread) {    // do something else  } else {    // throw an error? }

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