[self addSubview:self.instructionLabeLabel];
self.instructionLabeLabel.textAlignment = NSTextAlignmentCenter;
self.instructionLabeLabel.sd_layout
.topSpaceToView(self.mailBox, 15)
.centerXEqualToView(self)
.widthIs(500)
.autoHeightRatio(0);
【widthIs(500)】这里的500设置成父视图的宽或者写成最大宽度