iOS-systemLayoutSizeFittingSize获

    [self addSubview:self.evaluateTitleLbl];

    [_evaluateTitleLbl mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.equalTo(_evaluateTitle.mas_left);
        make.top.equalTo(_evaluateTitle.mas_bottom).offset(12);
        make.right.equalTo(self.mas_right).offset(-15);
    }];
CGfloat height =  [self.evaluateTitleLbl systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;

这里的height 就是获取布局后的 label 实际高度。