时间：   |   分类：     |   阅读： 323 字 ~2分钟

jQuery.sap.declare用于宣称一个模块已存在。

在OpenUI5开发指南–精粹–优化应用–模块化和依赖管理中对declare介绍是:

Modules can declare themselves by calling the static jQuery.sap.declare functionwith their name. This helpsSAPUI5tocheck at runtime whether a loaded module contains the expectedcontent by comparing the required name against the declared name.As a side effect,jQuery.sap.declare ensures that the parent namespace of the module name exists in the currentglobal namespace (window).Formore information, see jQuery.sap.declare.

For modules without declaration, the framework assumes that themodule has the expected content and declares it with the name thatwas used for loading. In some cases a module declaration ismandatory, see Avoiding Duplicates.

jQuery.sap.declare函数源码在jquery.sap.global.js，执行时可在sap-ui-core.js中找到。

通过下面的源代码可知，jQuery.sap.delcare首先通过ui5ToRJS将javascript类名转换为js文件名，例如sap.m.Dialog转换为sap/m/Dialog.js，然后执行declareModule函数。declareModule函数查找Core的mModules是否包含该模块且非初始状态，如果不包含该模块则添加模块并直接设为READY状态（说是避免循环？！！），且在_execStack为空时当作bootstrap模块加入_execStack。最后在bCreateNamespace不为false的情况下，执行jQuery.sap.getObject检查类的命名空间是否存在，不存在则创建。例如sap.m.Dialog，如果命名空间不存在的话，则创建window.sap={}，window.sap.m={}。

  var sNamespaceObj = sModuleName;

  // check for an object as parameter for sModuleName
  // in case of this the object contains the module name and the type
  // which could be {modName: "sap.ui.core.Dev", type: "view"}
  if (typeof (sModuleName) === "object") {
    sNamespaceObj = sModuleName.modName;
    sModuleName = ui5ToRJS(sModuleName.modName) + 
          (sModuleName.type ? "." + sModuleName.type : "") + ".js";
  } else {
    sModuleName = ui5ToRJS(sModuleName) + ".js";
  }

  declareModule(sModuleName);

  // ensure parent namespace even if module was declared already
  // (as declare might have been called by require)
  if (bCreateNamespace !== false) {
    // ensure parent namespace
    jQuery.sap.getObject(sNamespaceObj, 1);
  }

  return this;
};

function declareModule(sModuleName) {
  var oModule;

  // sModuleName must be a unified resource name of type .js
  jQuery.sap.assert(/\.js$/.test(sModuleName), "must be a Javascript module");

  oModule = mModules[sModuleName] || 
            (mModules[sModuleName] = { state : INITIAL });

  if ( oModule.state > INITIAL ) {
    return oModule;
  }

  if ( log.isLoggable() ) {
    log.debug(sLogPrefix + "declare module '" + sModuleName + "'");
  }

  // avoid cycles
  oModule.state = READY;

  // the first call to declareModule is assumed to identify the bootstrap module
  // Note: this is only a guess and fails e.g. when multiple modules are loaded 
  // via a script tag to make it safe, we could convert 'declare' calls to 
  // e.g. 'subdeclare' calls at build time.
  if ( _execStack.length === 0 ) {
    _execStack.push(sModuleName);
    oModule.url = oModule.url || _sBootstrapUrl;
  }

  return oModule;
}

一般在定制控件的js文件中，第一行就是通过jQuery.sap.declare宣称该控件已经存在了。

0%