代碼適配

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

#define MyUIScreen  375 // UI設(shè)計原型圖的手機尺寸寬度(6s), 6p的--414

@implementation UIFont (DXFont)

+ (void)load{
    
    //獲取替換后的類方法
    Method newMethod = class_getClassMethod([self class], @selector(adjustFont:));
    //獲取替換前的類方法
    Method method = class_getClassMethod([self class], @selector(systemFontOfSize:));
    //然后交換類方法
    method_exchangeImplementations(newMethod, method);
    
}

// 以6s未基準(zhǔn)（因為一般UI設(shè)計是以6s尺寸為基準(zhǔn)設(shè)計的）的字體伸眶。在5s和6P上會根據(jù)屏幕尺寸堡牡，字體大小會相應(yīng)的擴大和縮小
+ (UIFont *)adjustFont:(CGFloat)fontSize {
    UIFont *newFont = nil;
    newFont = [UIFont adjustFont:fontSize * [UIScreen mainScreen].bounds.size.width/MyUIScreen];
    return newFont;
}

@end

xib適配

#import "UILabel+DXFont.h"
#import <objc/runtime.h>

@implementation UILabel (DXFont)

+ (void)load{
    //利用running time運行池的方法在程序啟動的時候把兩個方法替換 適用Xib建立的label
    Method imp = class_getInstanceMethod([self class], @selector(initWithCoder:));
    Method myImp = class_getInstanceMethod([self class], @selector(myInitWithCoder:));
    method_exchangeImplementations(imp, myImp);  //交換方法
}

- (id)myInitWithCoder:(NSCoder*)aDecode{
    [self myInitWithCoder:aDecode];
    if (self) {
        CGFloat fontSize = self.font.pointSize;
        self.font = [UIFont systemFontOfSize:fontSize];
    }
    return self;
}

@end

#import "UIButton+DXFont.h"
#import <objc/runtime.h>

@implementation UIButton (DXFont)

+ (void)load{
    
    //利用running time運行池的方法在程序啟動的時候把兩個方法替換 適用Xib建立的label
    Method imp = class_getInstanceMethod([self class], @selector(initWithCoder:));
    Method myImp = class_getInstanceMethod([self class], @selector(myInitWithCoder:));
    method_exchangeImplementations(imp, myImp);  //交換方法
}

- (id)myInitWithCoder:(NSCoder*)aDecode{
    [self myInitWithCoder:aDecode];
    if (self) {
        CGFloat fontSize = self.titleLabel.font.pointSize;
        self.titleLabel.font = [UIFont systemFontOfSize:fontSize];
    }
    return self;
}

@end

參考文章：
http://www.reibang.com/p/8b8731ed84f8
http://www.reibang.com/p/0541caf7cecb