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我有 2 个向 Web 服务发送请求的视图控制器。接收到数据后，数据将保存到 Document 文件夹中的文件中。

这些是2个VC：

Live_VC：

#import "FV_Live_ViewController.h"

@interface FV_Live_ViewController ()
@end

@implementation FV_Live_ViewController

NSArray  *paths;
NSString *documentsDirectory;
NSString *path;

- (void)viewDidLoad {

paths              = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentsDirectory = [paths firstObject];

[self sendRequest];    // first request of data ("Live" data)
}

- (void)sendRequest {
// other code

// request of "Live" data
[urlRequest startWithCompletion:^(URLRequest *request, NSData *data, NSError *error, BOOL success) {
    if (success) {
        // other code

        NSString *filename = [NSString stringWithFormat:@"months.plist"];   
        path = [documentsDirectory stringByAppendingPathComponent:filename];    // path = "...\months.plist"

        // second request of data (monthly data) if months.plist doesn't exists
        if (![[NSFileManager defaultManager] fileExistsAtPath: path]) {
            [self sendMonthRequest];
        }
    }
}];
}    

- (void)sendMonthRequest {

[urlRequest startWithCompletion:^(URLRequest *request, NSData *data, NSError *error, BOOL success) {            
    if (success) {
        // other code

        [monthlyArray writeToFile: path atomically:YES];    // path should be "...\months.plist" while it is "...\yesterday.plist"
    }
}];
}

@end

今天_VC：

#import "FV_Today_ViewController.h"

@interface FV_Today_ViewController ()
@end

@implementation FV_Today_ViewController

NSArray  *paths;
NSString *documentsDirectory;
NSString *path;

- (void)viewDidLoad {

paths              = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentsDirectory = [paths firstObject];

[self sendRequest];        // first call of "sendRequest" to get today data
}

- (void)sendRequest {
//  other code

// request of "Today" data
[urlRequest startWithCompletion:^(URLRequest *request, NSData *data, NSError *error, BOOL success) {
    if (success) {       
        //  other code

        NSString *filename = [NSString stringWithFormat:@"today.plist"];
        path = [documentsDirectory stringByAppendingPathComponent:filename];    // path = "...\today.plist"

        [dataDictionary writeToFile: path atomically:YES];      // save data to today.plist

        // second call of "sendRequest" to get yesterday data only if yesterday.plist doesn't already exists)           
        filename = [NSString stringWithFormat:@"yesterday.plist"];
        path = [documentsDirectory stringByAppendingPathComponent:filename];    // path = "...\yesterday.plist"
        if (![[NSFileManager defaultManager] fileExistsAtPath:path])
            [self sendRequest];
    }
}];
}

@end

在每个 VC 中，我使用 NSString（“path”）来存储路径，但问题是在“sendMonthRequest”方法（Live_VC）中，路径的值是在另一个 VC（Today_VC）中设置的值。怎么可能？第一个 VC 中的 NSString 的值如何被第二个 VC 更改？

谢谢， 科拉多

4

1 回答 1

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你得到这个结果是因为你把“路径”放在文件的顶部，使它成为一个全局变量。用花括号括起来，然后它将是一个普通的 ivar，

@implementation FV_Today_ViewController {

NSArray  *paths;
NSString *documentsDirectory;
NSString *path;
}
于 2014-09-06T00:20:54.820 回答