iphone - 将英寸转换为厘米，反之亦然

Answer 1

The problem occurs because you use pointers in NSInteger and float. I have modified your method with the implementation for both cm and inches, as follows:

- (NSString *)returnRightMetric:(NSString *)theMeasure typeOfMetricUsed:(NSString *)metricType
{
    NSString *result = nil;

    if ([metricType isEqualToString:@"inches"]) {
        NSArray* theConvertion = [theMeasure componentsSeparatedByCharactersInSet:
                                  [NSCharacterSet characterSetWithCharactersInString:@"’”"]];
        NSInteger value1 = [theConvertion[0] intValue];
        NSInteger value2 = [theConvertion[1] intValue];

        float number = ((value1 * 12) + value2) * 2.54;
        result = [NSString stringWithFormat:@"%.02f cm", round(number * 100.0) / 100.0];


    } else if ([metricType isEqualToString:@"cm"]) {
        float value = [theMeasure floatValue];
        float number = value / 2.54;

        if (number > 12.0) {
            result = [NSString stringWithFormat:@"%i’%i”", (int)floor(number / 12.0), (int)number % 12];

        } else {
            result = [NSString stringWithFormat:@"0’%i”", (int)round(number)];
        }

    }

    NSLog(@"result: %@", result);
    return result;
}

Some Test:

[self returnRightMetric:@"5’11”" typeOfMetricUsed:@"inches"];
[self returnRightMetric:@"180.34 cm" typeOfMetricUsed:@"cm"];
[self returnRightMetric:@"0’11”" typeOfMetricUsed:@"inches"];
[self returnRightMetric:@"27.94 cm" typeOfMetricUsed:@"cm"];

The output:

result: 180.34 cm
result: 5’11”
result: 27.94 cm
result: 0’11”

Answer 2

NSArray* theConvertion = [theMeasure componentsSeparatedByCharactersInSet:
                          [NSCharacterSet characterSetWithCharactersInString:@"’”"]];
int value1 = [theConvertion[0] intValue];
int value2 = [theConvertion[1] intValue];

float number = ((value1 * 12) + value2) * 2.54;
NSString *formattedNumber = [NSString stringWithFormat:@"%.02f", (number/100)];

So in short you need to know the difference between native/primitive type's and reference types (type that use pointers this character --> *. This might help Link

Answer 3

After some testings from the last answer(from tolgamorf) here is the final version. To me it works perfectly.

- (NSString *)returnRightMetric:(NSString *)theMeasure typeOfMetricUsed:(NSString *)metricType
{
    NSString *result = nil;

    if ([metricType isEqualToString:@"inches"]) {  
        if ([theMeasure isEqualToString:@""]) {
            return @"0";
        }
        NSArray* theConvertion = [theMeasure componentsSeparatedByCharactersInSet:
                                  [NSCharacterSet characterSetWithCharactersInString:@"’”"]];
        NSInteger value1 = [theConvertion[0] intValue];
        NSInteger value2 = [theConvertion[1] intValue];

        float number = ((value1 * 12) + value2) * 2.54;
        result = [NSString stringWithFormat:@"%.0f cm", round(number * 100.0) / 100.0];


    } else if ([metricType isEqualToString:@"cm"]) {
        float value = [theMeasure floatValue];
        float number = value / 2.54;

        if (roundf( number) >= 12.0) {
            if ((int)round( number) % 12==0) {
                result = [NSString stringWithFormat:@"%i’%i”", (int)roundf(number / 12.0), (int)round( number) % 12];
            }else{
                result = [NSString stringWithFormat:@"%i’%i”", (int)floorf(number / 12.0), (int)round( number) % 12];
            }
        } else {
            result = [NSString stringWithFormat:@"0’%i”", (int)round(number)];
        }
    }
    NSLog(@"result: %@", result);
    return result;
}

Answer 4

For today we have useful API from HealthKit:

let cm_q = HKQuantity(unit: HKUnit(from: .centimeter), doubleValue: 180)
var inch_string = h_formatter.string(fromMeters: cm_q.doubleValue(for: HKUnit.meter()))

var inches_double = cm_q.doubleValue(for: HKUnit.inch())
let inch_q = HKQuantity(unit: HKUnit(from: .inch), doubleValue: inches_double)
var cm_d = inch_q.doubleValue(for: HKUnit(from: .centimeter))
var string = h_formatter.string(fromValue: cm_d, unit: .centimeter)

Just copy to Playground and play converting of values from cm to inches and back. The formatter configuration:

let h_formatter = LengthFormatter()
h_formatter.isForPersonHeightUse = true
h_formatter.unitStyle = .short

In the result we have:

180cm -> "5′ 10.866″" and back to 180cm

I hope it'll help.