为什么总是比预想的糟糕，目标View总是超出SuperView的范围

[yangdehui]

self.registerButton.sd_layout
.leftEqualToView(self)
.rightEqualToView(self.loginButton)
.topSpaceToView(self.findPasswordButton, 5)
.bottomSpaceToView(self, 20);

self.loginButton.sd_layout
.leftEqualToView(self.registerButton)
.rightEqualToView(self)
.topEqualToView(self.registerButton)
.bottomEqualToView(self.registerButton);