约束运算符 用法 用简单的表达式创建约束： view1. ignoreAutoresizingMask () view1. centerX =| view2. centerX + 10 view1. centerY =| 15 view1. width =| 100 // or view1. width =| 100 ... 200 view1. height =| view2. height / 2 + 20 ... view. width =| 100 view. width =| 200