我正在从 Dropbox 下载文件修订状态，基本上我将 Dropbox 中下载的修订号与本地 plist 中的修订号进行比较。

比较它们后，我想用 Dropbox 的修订号更改本地修订号。但它不起作用，我快要失去理智了。

我放置了一些标志和 NSlogs，它似乎替换了值，但在我调用相同的函数或再次启动应用程序后，我看到该值没有被替换。它一遍又一遍地给出相同的输出

    NSString* revisionLocal = [dicInner objectForKey:@"revision"];
    NSString* statusLocal = [dicInner objectForKey:@"status"];

    NSLog(@"revision  value before %@",revisionLocal);
    NSLog(@"status value before %@",statusLocal);

   //If revision has changed on dropbox, flag it as outdated on the local revision
                        if(![revisionLocal isEqualToString: dropBoxRevision] ){
                            [dicInner setValue:@"outdated" forKey:@"status"];
                            //But the revision is the latest
                            [dicInner setValue:dropBoxRevision forKey:@"revision"];
                            //[dicInner setValue:@"outdated" forKey:@"revision"];

                            NSLog(@"revision value %@",[dicInner objectForKey:@"revision"]);
                            NSLog(@"status value %@",[dicInner objectForKey:@"status"]);

所以这给了我输出:

revision  value before 4309efbbb7
status value before updated
revision value 4409efbbb7
status value outdated

完整代码为:

- (void)restClient:(DBRestClient *)client loadedMetadata:(DBMetadata *)metadata {

    //get the local revision
    NSDictionary * localRevisionDic = [FileUtils readPlistIntoDictionary:@"revision.plist"];

    NSString *fileRevString = [NSString alloc];
    //get the revision from Dropbox
    //NSString * dropboxRevision;
    if (metadata.isDirectory) { 
        NSLog(@"Folder '%@' contains:", metadata.path);
        for (DBMetadata *file in metadata.contents) {

            NSLog(@"\t%@", file.filename);
            //NSLog(@"\t%@", file.lastModifiedDate);
            NSLog(@"\t%@", file.rev ); 

            //Assign dropbox revision for this file
            //dropboxRevision = file.rev;
            //if no local revision.plist, entry will be added. Hence init here
            if (localRevisionDic==nil){
                localRevisionDic = [[NSMutableDictionary alloc]init];

            }
            //Otherwise go through each from dropbox and campare with local

            //From Dropbox
            NSString * dropBoxFileName = file.filename;
            NSString * dropBoxRevision = file.rev;

            fileRevString = file.rev;

            //if no local revision.plist entry is added for all other files
            //with status need_downloaded, and no revision
            if ([localRevisionDic count]==0){

                //Creating revision dictionary entry for agenda.plist
                NSDictionary * localRevisionDicDic = [[NSMutableDictionary alloc]init];
                //when agenda.plist revision entry is added update the revision while leaving status as "new" before downloading
                //will be updated accordingly if download fails
                [localRevisionDicDic setValue:@"new" forKey:@"status"];
                //Status is new but the revision is the latest
                [localRevisionDicDic setValue:dropBoxRevision forKey:@"revision"];

                [localRevisionDic setValue:localRevisionDicDic forKey:dropBoxFileName];

            }else{//If there is local revision.plist compare and update accordingly
                NSDictionary * dicInner = [localRevisionDic objectForKey:dropBoxFileName];
                //File name Found locally
                if (dicInner!=nil){
                    NSString* revisionLocal = [dicInner objectForKey:@"revision"];
                    NSString* statusLocal = [dicInner objectForKey:@"status"];

                    NSLog(@"revision  value before %@",revisionLocal);
                    NSLog(@"status value before %@",statusLocal);

                    //If revision has changed on dropbox, flag it as outdated on the local revision
                    if(![revisionLocal isEqualToString: dropBoxRevision] ){
                        [dicInner setValue:@"outdated" forKey:@"status"];
                        //But the revision is the latest
                        [dicInner setValue:dropBoxRevision forKey:@"revision"];
                        //[dicInner setValue:@"outdated" forKey:@"revision"];

                        NSLog(@"revision value %@",[dicInner objectForKey:@"revision"]);
                        NSLog(@"status value %@",[dicInner objectForKey:@"status"]);
                    }
                    }else{//File name not found locally newly added on dropbox

                        NSDictionary * localRevisionDicDic = [[NSMutableDictionary alloc]init];
                        //when agenda.plist revision entry is added update the revision while leaving status as "new" before downloading
                        //will be updated accordingly if download fails
                        [localRevisionDicDic setValue:@"new" forKey:@"status"];
                        //But the revision is the latest
                        [localRevisionDicDic setValue:dropBoxRevision forKey:@"revision"];

                        [localRevisionDic setValue:localRevisionDicDic forKey:dropBoxFileName];
                }
            }
        }
    }
    //At this point agendaRevisionDicTemp contains all the files in dropbox entered/updated.
    [[self agenda] setRevision:localRevisionDic];

    //*****The following block is needed to determine is new agenda is needed or not.
    BOOL newAgendaNeeded = false;

    NSMutableDictionary * agendaRevisionDicLocal = [localRevisionDic objectForKey:@"agenda.plist"];

    //NSString * localRevision = [agendaRevisionDicLocal objectForKey:@"revision"]; //what is this value?

    NSString * localStatus = [agendaRevisionDicLocal objectForKey:@"status"];
    NSLog(@"Local Status= %@",agendaRevisionDicLocal);


    if ([localStatus isEqualToString:@"new"] ||[localStatus isEqualToString:@"outdated"]){
        newAgendaNeeded = true;
        //when agenda.plist is added update the revision while leaving status as "new" before downloading
        //will be updated accordingly if download fails
        NSDictionary * agendaDic = [[[self agenda]revision] objectForKey:@"agenda.plist"];
        [agendaDic setValue:@"updated" forKey:@"status"];
        NSLog(@"agendaDic where update %@",agendaDic);

    }
    //*****The above block is needed to determine is new agenda is needed or not.

    //If new agenda is needed download
    if (newAgendaNeeded){
        //Download agenda.plist
        NSString *documentsDirectory = FileUtils.getDocumentsDirectory;
        [[self restClient] loadFile:@"/agenda.plist" intoPath: [ NSString stringWithFormat:@"%@/%@",documentsDirectory,@"agenda.plist"] ];

    } else{//Else display the scene

        [self populateSceneFromAgenda];

    }

    [restOfView reloadData];
    // Add at start of requestFinished AND requestFailed
    [MBProgressHUD hideHUDForView:self.view animated:YES];
}

知道如何替换该值吗？

最佳答案

您不尊重 NSDictionary 对象的不变性。您将 localRevisionDic 声明为 NSDictionary*，但稍后可以为其分配 NSMutableDictionary 的值。 localRevisionDicDic 声明为 NSDictionary* 但初始化为 NSMutableDictionary 的值。以下两个赋值应该在编译时被警告。在行

[localRevisionDic setValue:localRevisionDicDic forKey:dropBoxFileName];

谁能确定 localRevisionDic 是可变的还是不可变的？
然后，您再次将 dicInner 声明为 NSDictionary*，但稍后尝试设置 Value 两次。首先制作字典的可变副本。

关于objective-c - 无法更改/替换 NSDictionary 键值 IOS，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12695027/