using Study.DelegateSeries.Core.Calculator;
using System;
using System.Collections.Generic;
using System.Text;

namespace Study.DelegateSeries.Core
{
    /// <summary>
    /// 实例化委托
    /// </summary>
    public class InstanceDelegate
    {
        /// <summary>
        /// 基础语法
        /// (c#1.0 开始提供)
        /// </summary>
        public CalculatorDelegate BaseInstance()
        {
            CalculatorDelegate operation = new CalculatorDelegate(new Addition().Add);
            return operation;
        }

        /// <summary>
        /// c#2.0 简写方法
        /// (基于类型推断)
        /// </summary>
        public CalculatorDelegate AutoTypeInstance()
        {
            CalculatorDelegate operation = new Subtraction().Difference;
            return operation;
        }

        /// <summary>
        /// c#2.0 匿名委托
        /// (使用匿名方法实例化的委托)
        /// </summary>
        public CalculatorDelegate AnonymousInstance()
        {
            //c# 2.0基础语法
            CalculatorDelegate operation = delegate (decimal a, decimal b) { return (a * b) * (a * b); };
            return operation;
        }

        /// <summary>
        /// c#3.0 Lambda表达式
        /// (实质："Lambda表达式"是一个匿名函数)
        /// </summary>
        public CalculatorDelegate LambdaInstance()
        {
            CalculatorDelegate operation = (decimal a, decimal b) => { return a * a + b * b + 2 * a * b; };
            //自动推断
            CalculatorDelegate operation2 = (a, b) => { return a * a + b * b + 2 * a * b; };

            //{}只有一句时的简写
            CalculatorDelegate operation3 = (a, b) => a * a + b * b + 2 * a * b;

            return operation;
        }
    }
}