iOS字体大小适配的3种方法示例代码

//宏定义
#define SCREEN_WIDTH ([UIScreen mainScreen].bounds.size.width)
#define FONT_SIZE(size) ([UIFont systemFontOfSize:FontSize(size))


static inline CGFloat FontSize(CGFloat fontSize){
 if (SCREEN_WIDTH==320) {
  return fontSize-2;
 }else if (SCREEN_WIDTH==375){
  return fontSize;
 }else{
  return fontSize+2;
 }
}

#define IsIphone6P   SCREEN_WIDTH==414
#define SizeScale   (IsIphone6P ? 1.5 : 1)
#define kFontSize(value) value*SizeScale
#define kFont(value)  [UIFont systemFontOfSize:value*SizeScale]

#define MyUIScreen 375 // UI设计原型图的手机尺寸宽度(6), 6p的--414

UIFont+runtime.m

#import "UIFont+runtime.h"
#import <objc/runtime.h>

@implementation UIFont (runtime)

+ (void)load {
 // 获取替换后的类方法
 Method newMethod = class_getClassMethod([self class], @selector(adjustFont:));
 // 获取替换前的类方法
 Method method = class_getClassMethod([self class], @selector(systemFontOfSize:));
 // 然后交换类方法，交换两个方法的IMP指针，(IMP代表了方法的具体的实现）
 method_exchangeImplementations(newMethod, method);
}

+ (UIFont *)adjustFont:(CGFloat)fontSize {
 UIFont *newFont = nil;
 newFont = [UIFont adjustFont:fontSize * [UIScreen mainScreen].bounds.size.width/MyUIScreen];
 return newFont;
}
@end

Controller类中正常调用就行了：
UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(0, 150, [UIScreen mainScreen].bounds.size.width, 60)];
label.text = @"iOS字体大小适配";
label.font = [UIFont systemFontOfSize:16];
[self.view addSubview:label];