用位移位评估枚举

Question

我现在不太了解移位如何工作。给定以下枚举，if statement如何确定为真？

typedef NS_OPTIONS(uint16_t, flags) {
    flagsFirst   = 1 << 0,
    flagsSecond  = 1 << 1,
    flagsThird   = 1 << 2,
    flagsFourth  = 1 << 3
};


if (flags & flagsThird) {
    // ... 
}