为什么不在salesforce中使用可调度类？

Question

当我从apex页面调用createCurrencies（）方法as action =“{！createCurrencies}”时，以下代码正常工作 但是当我安排它时，它无法正常工作。

你知道可能出现什么问题吗？

global class DailyExchangeRates implements Database.Batchable<sObject>, Schedulable {

global Database.QueryLocator start(Database.BatchableContext BC){return null;}

global void execute(Database.BatchableContext BC, list<sObject> scope){}

global void finish(Database.BatchableContext BC){}

global void execute(SchedulableContext SC) {
    createCurrencies();
}

public void createCurrencies(){
    if(getRate(eur, fb).length() <= 6 && getRate(eur, fb).length() > 0){
        Double EurTl = Double.valueOf(getRate(eur, fb));
        Double GbpTl = Double.valueOf(getRate(gbp, fb));
        Double UsdTl = Double.valueOf(getRate(usd, fb));
        Double RubTl = Double.valueOf(getRate(rub, fb));
        insert new Currency__c(                 
            Conversion_Rate__c = EurTl,             
            Currency_Date__c = effectiveDate, 
            Published_Date__c = getTcmbDate(),
            Exchange_Type__c = 'EURMA'
            );
        insert new Currency__c(                 
            Conversion_Rate__c = GbpTl,             
            Currency_Date__c = effectiveDate, 
            Published_Date__c = getTcmbDate(),
            Exchange_Type__c = 'GBPMA'
            );
        insert new Currency__c(                 
            Conversion_Rate__c = UsdTl,             
            Currency_Date__c = effectiveDate, 
            Published_Date__c = getTcmbDate(),
            Exchange_Type__c = 'USDMA'
            );
        insert new Currency__c(                 
            Conversion_Rate__c = RubTl,             
            Currency_Date__c = effectiveDate, 
            Published_Date__c = getTcmbDate(),
            Exchange_Type__c = 'RUBMA'
            );        
    }
}

}