ARC语义问题，没有可见的界面错误

Question

我的实现文件中有一个错误，该错误不断标记，但我似乎无法修复。我已经注释掉了错误。我该如何修复这个错误？

#import "FilmSearchService.h"


@implementation FilmSearchService
@synthesize searchTerm;
@synthesize delegate;

@synthesize results;
-(void)main {
    NSString *api_key = @"1234";
    NSString *search_term = [searchTerm stringByAddingPercentEscapeUsingEncoding:NSASCIIStringEncoding]; // no visible @ interface for 'NSString' declares the selector 'stringByAddingPercentEscapeUsingEncoding'
    NSString *url = [NSString stringWithFormat:@"http://api.rottentomatoes.com/api/public/v1.0/movies.json?apikey=%@&q=%@", api_key, search_term];

    NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:url]
                                              cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
    NSData *responseData = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:nil error:nil];

    if (responseData != nil) {
        NSError *error = nil;
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];

        if (error) {
            [delegate serviceFinished:self withError:YES];
        } else {
            results = (NSArray *) [json valueForKey:@"movies"];
            [delegate serviceFinished:self withError:NO];
        }
    } else {
        [delegate serviceFinished:self withError:YES];
    }
}@end

电影搜索服务头文件：

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import "ServiceDelegate.h"

@interface FilmSearchService : NSOperation
{
    NSString *searchTerm;
    id<ServiceDelegate> delegate;
    NSArray *results;
}

@property (nonatomic, retain) NSString *searchTerm;
@property (nonatomic, retain) id<ServiceDelegate> delegate;

@property (nonatomic, retain) NSArray *results;


@end

如果这是一个相对简单的问题需要解决，我深表歉意，我对 Objective C 还很陌生，希望您能耐心等待。

谢谢你。

Answer 1

字符串方法是 stringByAddingPercentEscape*s*UsingEncoding 不是 stringByAddingPercentEscapeUsingEncoding

Answer 2

@ExitToShell 是正确的。编译器显然对该字符串方法的拼写错误感到不满。这是“书面示例”：

NSString *search_term = [searchTerm stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];

注意它没有说

stringByAddingPercentEscapeUsingEncoding

，这不是字符串上的方法。