How to check open task for a particular opportunity

Dear Amol,

In order to implement such logic, please, create a replacing client module for the opportunity page. 

Afterwards, in the method section you need to add logic. Firstly, every time you go from one stage to another the page gets reloaded. Threrfore, we need to interfere to the save method and check, if the needed field is filled in. If not, then do not save. In the example below we are checking if Email field is filled in. Please use it as an example for your opportunity page business task.

define("LeadPageV2", ["LeadPageResources"], function(resources) {
	return {
		entitySchemaName: "Lead",
		attributes: {
			"OldStatus": {
				type: Terrasoft.ViewModelColumnType.VIRTUAL_COLUMN,
				dataValueType: Terrasoft.DataValueType.CUSTOM_OBJECT,
				value: ""
			},
			"CustomerAgree": {
				type: Terrasoft.ViewModelColumnType.VIRTUAL_COLUMN,
				dataValueType: Terrasoft.DataValueType.BOOLEAN,
				value: false
			}
		},
		diff: /**SCHEMA_DIFF*/[]/**SCHEMA_DIFF*/,
		methods: {
			onEntityInitialized: function() {
				this.callParent(arguments);
				this.set("OldStatus", this.get("QualifyStatus"));
			},
			save: function() {
				if (this.get("OldStatus").value !== this.get("QualifyStatus").value) {
					if (this.get("Email")) {
						if (this.get("CustomerAgree") === true) {
							this.callParent(arguments);
							this.set("OldStatus", this.get("QualifyStatus"));
						} else {
							var scope = this;
							this.showConfirmationDialog("Are you sure?",
							function(returnCode) {
								if (returnCode === Terrasoft.MessageBoxButtons.YES.returnCode) {
									scope.set("CustomerAgree", true);
									scope.save();
								} else {
									this.set("QualifyStatus", this.get("OldStatus"));
								}
							}, ["yes", "no"]);
						}
					} else {
						this.showInformationDialog("Please insert the Email");
						this.set("QualifyStatus", this.get("OldStatus"));
						return false;
					}
				} else {
					this.callParent(arguments);
				}
			},
			onSaved: function() {
				this.callParent(arguments);
				this.set("CustomerAgree", false);
			}
		},
		rules: {}
	};
});