UIImageView+WebCache這個類別是我們常用到的蒲祈，我相信絕大部分的程序員都看過其中的內(nèi)容,直接上代碼
- (void)sd_setImageWithURL:(nullable NSURL *)url
- (void)sd_setImageWithURL:(nullable NSURL *)url
placeholderImage:(nullable UIImage *)placeholder
- (void)sd_setImageWithURL:(nullable NSURL *)url
placeholderImage:(nullable UIImage *)placeholder
options:(SDWebImageOptions)options
- (void)sd_setImageWithURL:(nullable NSURL *)url
completed:(nullable SDExternalCompletionBlock)completedBlock
- (void)sd_setImageWithURL:(nullable NSURL *)url
placeholderImage:(nullable UIImage *)placeholder
completed:(nullable SDExternalCompletionBlock)completedBlock
- (void)sd_setImageWithURL:(nullable NSURL *)url
placeholderImage:(nullable UIImage *)placeholder
options:(SDWebImageOptions)options
completed:(nullable SDExternalCompletionBlock)completedBlock
- (void)sd_setImageWithPreviousCachedImageWithURL:(nullable NSURL *)url
placeholderImage:(nullable UIImage *)placeholder
options:(SDWebImageOptions)options
progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
completed:(nullable SDExternalCompletionBlock)completedBlock
這里的設(shè)計思路值得我們學習，當你寫一個對外的接口或者方法的時候台夺，可以根據(jù)不能的需求定制不同的方法，這樣可以滿足不同需求的人痴脾，而且顯得美觀和整潔颤介。
- (void)sd_setAnimationImagesWithURLs:(nonnull NSArray<NSURL *> *)arrayOfURLs {
[self sd_cancelCurrentAnimationImagesLoad];
__weak __typeof(self)wself = self;
NSPointerArray *operationsArray = [self sd_animationOperationArray];
//這個方法,遍歷字典和量大的數(shù)組和遍歷字典時性能比 for in 好,且代碼更加優(yōu)雅;對于單個數(shù)組使用for in 新能更好
[arrayOfURLs enumerateObjectsUsingBlock:^(NSURL *logoImageURL, NSUInteger idx, BOOL * _Nonnull stop) {//遍歷urls
id <SDWebImageOperation> operation = [[SDWebImageManager sharedManager] loadImageWithURL:logoImageURL options:0 progress:nil completed:^(UIImage *image, NSData *data, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
if (!wself) return;
dispatch_main_async_safe(^{
__strong UIImageView *sself = wself;
[sself stopAnimating];
if (sself && image) {
NSMutableArray<UIImage *> *currentImages = [[sself animationImages] mutableCopy];//處理gif圖像
if (!currentImages) {
currentImages = [[NSMutableArray alloc] init];
}
// We know what index objects should be at when they are returned so
// we will put the object at the index, filling any empty indexes
// with the image that was returned too "early". These images will
// be overwritten. (does not require additional sorting datastructure)
while ([currentImages count] < idx) { //若gif圖片將靜態(tài)數(shù)組添加到數(shù)組中
[currentImages addObject:image];
}
currentImages[idx] = image;
sself.animationImages = currentImages;
[sself setNeedsLayout];
}
[sself startAnimating];
});
}];
@synchronized (self) {
[operationsArray addPointer:(__bridge void *)(operation)]; //添加operation
}
}];
}
static char animationLoadOperationKey;
// element is weak because operation instance is retained by SDWebImageManager's runningOperations property
// we should use lock to keep thread-safe because these method may not be acessed from main queue
- (NSPointerArray *)sd_animationOperationArray {
@synchronized(self) {
NSPointerArray *operationsArray = objc_getAssociatedObject(self, &animationLoadOperationKey);//關(guān)聯(lián)對象
if (operationsArray) {
return operationsArray;
}
operationsArray = [NSPointerArray weakObjectsPointerArray]; //建立弱連接
objc_setAssociatedObject(self, &animationLoadOperationKey, operationsArray, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
return operationsArray;
}
}
- (void)sd_cancelCurrentAnimationImagesLoad {
NSPointerArray *operationsArray = [self sd_animationOperationArray];
if (operationsArray) {
@synchronized (self) {//同步鎖，防止多線程同時訪問
for (id operation in operationsArray) {
if ([operation conformsToProtocol:@protocol(SDWebImageOperation)]) { // operation 是否遵守SDWebImageOperation協(xié)議
[operation cancel]; //取消
}
}
operationsArray.count = 0;
}
}
}
擴展知識
1.NSMapTable赞赖， NSHashTable NSPointerArray
現(xiàn)在我們雖然都在用ARC,但是有時候我們需要精確的知道我們是不是在dic滚朵，set，和array中持有還是不持有對象前域，但是NSDictionary辕近，NSSet，NSArray匿垄，所以我們需要NSMapTable移宅， NSHashTable NSPointerArray
以NSPointerArray為例
+ (NSPointerArray *)strongObjectsPointerArray //建立強連接
+ (NSPointerArray *)weakObjectsPointerArray //建立弱連接
- enumerateObjectsUsingBlock 這個方法,遍歷字典和量大的數(shù)組和遍歷字典時性能比 for in 好,且代碼更加優(yōu)雅;對于單個數(shù)組使用for in 新能更好 在很多框架中都被使用，以利用到多核cpu的優(yōu)勢
用法：
NSArray 和 NSSet 都可以使用
- (void)enumerateObjectsUsingBlock:(void (NS_NOESCAPE ^)(ObjectType obj, NSUInteger idx, BOOL *stop))block
- (void)enumerateObjectsWithOptions:(NSEnumerationOptions)opts usingBlock:(void (NS_NOESCAPE ^)(ObjectType obj, NSUInteger idx, BOOL *stop))block
NSDictionary 使用
- (void)enumerateKeysAndObjectsUsingBlock:(void (NS_NOESCAPE ^)(KeyType key, ObjectType obj, BOOL *stop))block
- (void)enumerateKeysAndObjectsWithOptions:(NSEnumerationOptions)opts usingBlock:(void (NS_NOESCAPE ^)(KeyType key, ObjectType obj, BOOL *stop))block
NSEnumerationConcurrent 順序
NSEnumerationReverse 倒序
例子：
NSArray :
NSArray *array = @[@"a", @"b", @"c"];
for (NSString *str in [array reverseObjectEnumerator]) { //reverseObjectEnumerator倒序 objectEnumerator 正序
}
[array enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(Sark *sark, NSUInteger idx, BOOL *stop) {
}];
NSDictionary:
NSDictionary *dict = @{@"a": @"1", @"b": @"2"};
[dict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
NSLog(@"key: %@, value: %@", key, obj);
}];
**
遍歷執(zhí)行block會分配在多核cpu上執(zhí)行椿疗，底層可能是GCD的并發(fā)queue漏峰，對于耗時的任務(wù)來說是不錯的選擇，同事届榄，對于遍歷的外部是保持同步的芽狗，遍歷都完成后才繼續(xù)執(zhí)行下一行。
**
