iOS開發之swift版非同步載入網路圖片

    與SDWebImage非同步載入網路圖片的功能相似，只是程式碼比較簡單，功能沒有SD的完善與強大，支援預設新增圖片，支援本地快取。

     非同步載入圖片的核心程式碼如下：

 func setZYHWebImage(url:NSString?, defaultImage:NSString?, isCache:Bool){
        var ZYHImage:UIImage?
        if url == nil {
            return
        }
        //設定預設圖片
        if defaultImage != nil
 
 {
            self.image=UIImage(named: defaultImage!)
        }
        //是否進行快取處理
        if isCache {
        //快取管理類
            var data:NSData?=ZYHWebImageChcheCenter.readCacheFromUrl(url!)
            if data != nil {
                ZYHImage=UIImage(data: data!)
                self.image=ZYHImage
            }else
 
{
            //獲取非同步執行緒
               var dispath=dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)
                dispatch_async(dispath, { () -> Void in
                    var URL:NSURL = NSURL(string: url!)!
                    var data:NSData?=NSData(contentsOfURL: URL)
                    if
 
 data != nil {
                        ZYHImage=UIImage(data: data!)
                        //寫快取
                        ZYHWebImageChcheCenter.writeCacheToUrl(url!, data: data!)
                        //主執行緒中重新整理UI
                        dispatch_async(dispatch_get_main_queue(), { () -> Void in
                            //重新整理主UI
                            self.image=ZYHImage
                        })
                    }
                    
                })
            }
        }else{
            var dispath=dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)
            dispatch_async(dispath, { () -> Void in
                var URL:NSURL = NSURL(string: url!)!
                var data:NSData?=NSData(contentsOfURL: URL)
                if data != nil {
                    ZYHImage=UIImage(data: data!)
                    //寫快取
                    dispatch_async(dispatch_get_main_queue(), { () -> Void in
                        //重新整理主UI
                        self.image=ZYHImage
                    })
                }
                
            })
        }
    }
    
}

快取的處理這裡採用的是寫檔案的方式，通過檔名來對快取進行管理，這個框架還不完善，後面會加入快取清除等功能。快取的核心程式碼如下：

classfuncreadCacheFromUrl(url:NSString)->NSData?{
        var data:NSData?
        var path:NSString=ZYHWebImageChcheCenter.getFullCachePathFromUrl(url)
        if NSFileManager.defaultManager().fileExistsAtPath(path) {
            data=NSData.dataWithContentsOfMappedFile(path) as? NSData
        }
        return data
    }
    
    classfuncwriteCacheToUrl(url:NSString, data:NSData){
        var path:NSString=ZYHWebImageChcheCenter.getFullCachePathFromUrl(url)
       println(data.writeToFile(path, atomically: true))
    }
    //設定快取路徑
    classfuncgetFullCachePathFromUrl(url:NSString)->NSString{
        var chchePath=NSHomeDirectory().stringByAppendingString("/Library/Caches/MyCache")
        var fileManager:NSFileManager=NSFileManager.defaultManager()
        fileManager.fileExistsAtPath(chchePath)
        if !(fileManager.fileExistsAtPath(chchePath)) {
            fileManager.createDirectoryAtPath(chchePath, withIntermediateDirectories: true, attributes: nil, error: nil)
        }
        //進行字串處理
        var newURL:NSString
        newURL=ZYHWebImageChcheCenter.stringToZYHString(url)
        chchePath=chchePath.stringByAppendingFormat("/%@", newURL)
        return chchePath
    }
    
    classfuncstringToZYHString(str:NSString)->NSString{
        var newStr:NSMutableString=NSMutableString()
        for var i:NSInteger=0; i < str.length; i++ {
            var c:unichar=str.characterAtIndex(i)
            if (c>=48&&c<=57)||(c>=65&&c<=90)||(c>=97&&c<=122){
                newStr.appendFormat("%c", c)
            }
        }
        return newStr.copy() as NSString
        
    }

因xcode的版本不同，swift語言語法隨環境時常會變化，此版本在6.1中可用，更高版本中需要修改少部分即可。