将字段添加到NSMutableURLRequest

Question

如何将键值对添加到NSMutableURLRequest的主体？我知道我可以使用这样的东西:

NSURL *url = [[NSURL alloc] initWithString:@"http://localhost:8080/upload/"];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:@"POST"];
NSString *bodyContents = @"fileName=";
[bodyContents stringByAppendingString:fileName];
[bodyContents stringByAppendingString:@"&"];
[bodyContents stringByAppendingString:@"deviceName="];
[bodyContents stringByAppendingString:deviceName];
[bodyContents stringByAppendingString:@"fileContents="];
[bodyContents stringByAppendingString:fileContents];

但这似乎很麻烦,特别是如果我到达我需要在请求中提交大量值的地方.我希望苹果能提供类似[request addBodyField:@"fileName":fileName]或同样有用的方法,但我无法在文档中找到.有没有我遗失或者我只是坚持附加字符串？

Answer 1

问题是stringByAppendingString不会修改字符串,而是返回包含结果的新字符串.但是,您没有将结果分配stringByAppendingString给任何变量,并bodyContents保持不变.

要解决这个问题,您可以使用stringWithFormat:

NSString *bodyContents = [NSString stringWithFormat:@"fileName=%@&deviceName=%@fileContents=%@", fileName, deviceName, fileContents];

或者声明stringWithFormat为可变字符串并使用以下方法appendString:

NSMutableString *bodyContents = @"fileName=";
[bodyContents appendString:fileName];
[bodyContents appendString:@"&"];
// ...

或分配的结果stringWithFormat来bodyContents在每一个电话:

NSString *bodyContents = @"fileName=";
bodyContents = [bodyContents stringByAppendingString:fileName];
bodyContents = [bodyContents stringByAppendingString:@"&"];
// ...

Answer 2

这里有很多好的答案.这就是我做的:我构建了一个参数类,它负责配对语法和url编码.

#import "NSString+URLEncoding.h"

@interface UrlParameter ()

@property (strong, nonatomic) NSString *pair;
@property (strong, nonatomic) NSString *encodedPair;

@end

@implementation UrlParameter

@synthesize pair = _pair;
@synthesize encodedPair = _encodedPair;


+ (UrlParameter *)withName:(NSString *)name value:(NSString *)value {

    UrlParameter *answer = [[UrlParameter alloc] init];
    answer.pair = [NSString stringWithFormat:@"%@=%@", name, value];
    answer.encodedPair = [NSString stringWithFormat:@"%@=%@", [name urlEncode], [value urlEncode]];

    return answer;  // autorelease if non-ARC
}

@end

这依赖于我在几篇文章中拼凑出来的NSString类别方法.(还准备好ARC):

@implementation NSString (URLEncoding)

- (NSString *)urlEncodeUsingEncoding:(CFStringEncoding)encoding {

    return CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                                               (__bridge CFStringRef)self,
                                                               NULL,
                                                               CFSTR("!*'();:@&=+$,/?%#[]"),
                                                               encoding));
}

- (NSString *)urlEncode {
    return [self urlEncodeUsingEncoding:kCFStringEncodingUTF8];
}

@end

我也是URL请求的子类,并给它可变的参数数组,然后,在它启动之前,它执行以下操作:

// in the interface
@property (strong, nonatomic) NSMutableArray *parameters;

- (void)prepareParameters {

    NSMutableString *encodedParameterPairs = [NSMutableString stringWithCapacity:256];

    int position = 1;
    for (UrlParameter *requestParameter in self.parameters) {
        [encodedParameterPairs appendString:[requestParameter encodedPair]];
        if (position < [self.parameters count]) [encodedParameterPairs appendString:@"&"];
        position++;
    }

    if ([[self HTTPMethod] isEqualToString:@"GET"] || [[self HTTPMethod] isEqualToString:@"DELETE"]) {

        NSString *urlString = [NSString stringWithFormat:@"%@?%@", [self URLString], encodedParameterPairs];
        [self setURL:[NSURL URLWithString:urlString]];

    } else {

        // POST, PUT
        NSData *postData = [encodedParameterPairs dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
        [self setHTTPBody:postData];
        [self setValue:[NSString stringWithFormat:@"%d", [postData length]] forHTTPHeaderField:@"Content-Length"];
        [self setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
    }
}