A member initializer that specifes an object initializer after the equals sign is an initialization of an embedded object. 成员构造者特指某个等号后面的对象构造者,是内嵌对象的初始化。
Add the value on the right side of the equal sign to the current value that is contained in the variable on the left side of the equal sign. 将等号右侧的值添加到等号左侧的变量中包含的当前值。