问题

设计师同学说有个标题的字体应该加粗，需要修改下。

解决

检查后发现代码中忽略了字体的粗细属性。

UIFont *font = [UIFont systemFontOfSize:fontSize];

这个方法是不支持设置字体粗细的。实际上系统提供了设置字体的粗细的方法。

+ (UIFont *)boldSystemFontOfSize:(CGFloat)fontSize;
+ (UIFont *)systemFontOfSize:(CGFloat)fontSize weight:(UIFontWeight)weight NS_AVAILABLE_IOS(8_2);

需要注意的是下面这个weight设置的方法只是在iOS8.2开始的版本生效。修改后设置字体的方法如下：

if(([[[UIDevice currentDevice] systemVersion] compare:@"8.2" options:NSNumericSearch] == NSOrderedAscending)) {
                font = [UIFont systemFontOfSize:fontSize];
            } else {
                font = [UIFont systemFontOfSize:fontSize weight:textWeight];
            }

扩展

fontWeight是描述字体粗细程度的属性，我们平时比较少注意到。另外iOS中定义了UIFontWeight的一些常量

UIKIT_EXTERN const UIFontWeight UIFontWeightUltraLight NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightThin NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightLight NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightRegular NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightMedium NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightSemibold NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightBold NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightHeavy NS_AVAILABLE_IOS(8_2);
UIKIT_EXTERN const UIFontWeight UIFontWeightBlack NS_AVAILABLE_IOS(8_2);