runtime MethodSwizzle 实践之扩展 NIAttributedLabel

runtime MethodeSwizzle 提供 简单的方法交换已知类的  Method IMP.

Method 可以是 外部可访问的 public 或者 private Method .所谓的属性或私有变量 也不过是 getter/setter Method 而已。

MethodeSwizzle 技术 几乎可以实现你要使用 已知类的所有东西。

so Powerful。

代码实现：

#import <Foundation/Foundation.h>

@interface NSObject (Swizzle)
+ (void)swizzleInstanceSelector:(SEL)originalSelector
                withNewSelector:(SEL)newSelector;
@end

#import "NSObject+Swizzle.h"
#import <objc/runtime.h>

@implementation NSObject (Swizzle)
+ (void) swizzleInstanceSelector:(SEL)originalSelector
                 withNewSelector:(SEL)newSelector
{
    Method originalMethod = class_getInstanceMethod(self, originalSelector);
    Method newMethod = class_getInstanceMethod(self, newSelector);

    BOOL methodAdded = class_addMethod([self class],
                                       originalSelector,
                                       method_getImplementation(newMethod),
                                       method_getTypeEncoding(newMethod));

    if (methodAdded) {
        class_replaceMethod([self class],
                            newSelector,
                            method_getImplementation(originalMethod),
                            method_getTypeEncoding(originalMethod));
    } else {
        method_exchangeImplementations(originalMethod, newMethod);
    }
}
@end

考虑通用性，这里使用NSObject 分类实现。

MethodeSwizzle 应用之解决实际问题：

最近使用

NIAttributedLabel 实现 文本渲染，图文混排等功能。还是挺不错的。

它提供简单的方法实现 插入文本链接， 设置delegate 回调 处理链接动作。

NIAttributedLabel.m 内部实现，

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event

并在

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

中检测是否触发链接，并触发回调。

///////////////////////////////////////////////////////////////////////////////////////////////////
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
  [super touchesEnded:touches withEvent:event];

  [self.longPressTimer invalidate];
  self.longPressTimer = nil;

  UITouch* touch = [touches anyObject];
  CGPoint point = [touch locationInView:self];

  if (nil != self.originalLink) {
    if ([self isPoint:point nearLink:self.originalLink]) {
      // This old-style method is deprecated, please update to the newer delegate method that supports
      // more data types.
      NIDASSERT(![self.delegate respondsToSelector:@selector(attributedLabel:didSelectLink:atPoint:)]);

      if ([self.delegate respondsToSelector:@selector(attributedLabel:didSelectTextCheckingResult:atPoint:)]) {
        [self.delegate attributedLabel:self didSelectTextCheckingResult:self.originalLink atPoint:point];
      }
    }
  }

  self.touchedLink = nil;
  self.originalLink = nil;

  [self setNeedsDisplay];
}

其中

 if (nil != self.originalLink) {
    if ([self isPoint:point nearLink:self.originalLink]) { 其中

self.originalLink 用方法

///////////////////////////////////////////////////////////////////////////////////////////////////
- (NSTextCheckingResult *)linkAtPoint:(CGPoint)point {
  if (!CGRectContainsPoint(CGRectInset(self.bounds, 0, -kVMargin), point)) {
    return nil;
  }

  CFArrayRef lines = CTFrameGetLines(self.textFrame);
  if (!lines) return nil;
  CFIndex count = CFArrayGetCount(lines);

  NSTextCheckingResult* foundLink = nil;

  CGPoint origins[count];
  CTFrameGetLineOrigins(self.textFrame, CFRangeMake(0,0), origins);

  CGAffineTransform transform = [self _transformForCoreText];
  CGFloat verticalOffset = [self _verticalOffsetForBounds:self.bounds];

  for (int i = 0; i < count; i++) {
    CGPoint linePoint = origins[i];

    CTLineRef line = CFArrayGetValueAtIndex(lines, i);
    CGRect flippedRect = [self getLineBounds:line point:linePoint];
    CGRect rect = CGRectApplyAffineTransform(flippedRect, transform);

    rect = CGRectInset(rect, 0, -kVMargin);
    rect = CGRectOffset(rect, 0, verticalOffset);

    if (CGRectContainsPoint(rect, point)) {
      CGPoint relativePoint = CGPointMake(point.x-CGRectGetMinX(rect),
                                          point.y-CGRectGetMinY(rect));
      CFIndex idx = CTLineGetStringIndexForPosition(line, relativePoint);
      foundLink = [self linkAtIndex:idx];
      if (foundLink) {
        return foundLink;
      }
    }
  }
  return nil;
}

获得。

这两个条件成立，则触发链接，否则就返回了。？？

实际情况可能是 我要检测 链接是否触发，没有触发的话我要自定义动作。

而且这两个方法还都是  NIAttributedLabel 类得私有方法， 举步维艰之际想到了强大的MethodSwizzle

思路：在分类中 定义两个函数  然后分别与 NIAttributedLabel  中的以上两个方法 调换。

#import "NIAttributedLabel+XYNIAttributedLabel.h"
#import <objc/runtime.h>
#import "NSObject+XYSwizzle.h"
@implementation NIAttributedLabel (XYNIAttributedLabel)

+(void)load{
    [self swizzleInstanceSelector:@selector(linkAtPoint:) withNewSelector:@selector(swizzleLinkAtPoint:)];
    [self swizzleInstanceSelector:@selector(isPoint:nearLink:) withNewSelector:@selector(swizzleIsPoint:nearLink:)];
}
-(BOOL)isTriggerLink:(CGPoint )point{
    NSTextCheckingResult *textCheckingResult = [self swizzleLinkAtPoint:point];
    if (nil != textCheckingResult) {
        if ([self swizzleIsPoint:point nearLink:textCheckingResult]) {
            return YES;
        }
    }
    return NO;
}

-(NSTextCheckingResult *)swizzleLinkAtPoint:(CGPoint)point{
    return  [self swizzleLinkAtPoint:point];
}

-(BOOL)swizzleIsPoint:(CGPoint)point nearLink:(NSTextCheckingResult *)link{
    BOOL resulte = [self swizzleIsPoint:point nearLink:link];
    return resulte;
}
@end

：上面

+(void)load 方法中 linkAtPoint 、isPoint:nearLink: 有可能会报编译器警告。无法找到相关sel ，因为它们是私有方法。不要理他，这个是在runtime 生效。我在demo 里有警告，但到了项目里好像没有了。不管它吧。

并提供

-(BOOL)isTriggerLink:(CGPoint )point; 对外调用 检测是否触发链接。

so。 问题得意 轻松解决。

废话一句： 实例方法 在 类对象中保持。

+(void)load{
    [self swizzleInstanceSelector:@selector(linkAtPoint:) withNewSelector:@selector(swizzleLinkAtPoint:)];
    [self swizzleInstanceSelector:@selector(isPoint:nearLink:) withNewSelector:@selector(swizzleIsPoint:nearLink:)];
}

以上解决方案有一定风险，如果被交换的NIAttributedLabel 方法名字被作者修改，项目又重新更新了库，则没有效果。