panda.el.opt.logic.QuestionSelectOpt Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of panda-core Show documentation

Panda Core is the core module of Panda Framework, it contains commonly used utility classes similar to apache-commons.

There is a newer version: 1.8.0

package panda.el.opt.logic;

import panda.el.ELContext;
import panda.el.ELException;
import panda.el.opt.AbstractTwoOpt;

/**
 * 三元运算符: ':' 

 * 说明,三元表达式包含两个运算符:'?',':'.整个表达式的结果由它们共同完成.而每个符号承担一部分操作.

 * '?':包含两个操作对象,即,'?'左侧的逻辑表达式,与'?'右侧的第一值.
 ':':也包含两个操作对象,即,':'前面生成的'?'对象,与':'右侧的第二个值.

 * 在进行运算的时候,是先运算':',而':'中将条件的判断委托到'?'当中.然后':'对象根据'?'中的返回 结果分别读取'?'中的的左值或,':'的右值
 */
public class QuestionSelectOpt extends AbstractTwoOpt {
	public int getPriority() {
		return 13;
	}

	public Object calculate(ELContext ec) {
		if (!(left instanceof QuestionOpt)) {
			throw new ELException("三元表达式错误!");
		}
		
		QuestionOpt qo = (QuestionOpt)left;
		Boolean cval = (Boolean)qo.calculate(ec);
		if (cval) {
			return qo.getRight(ec);
		}
		return getRight(ec);
	}

	public String operator() {
		return ":";
	}

}