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1 [up](../../../../tree/master/Guides/sample_code), [next](indexes.md)
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2
3 Number formatting
4 =================
5
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6 For the purpose of demonstration, we'll render the value 0.5 as a *raw* number, as a percentage, and as a *decimal*. For instance, on a French system, we'll get the following output:
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7
8 raw: 0.5
9 percent: 50 %
10 decimal: 0,5
11
12
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13 In a genuine Mustache way
14 -------------------------
15
16 Mustache is a simple template language. This is why there are so many [other Mustache implementations](https://github.com/defunkt/mustache/wiki/Other-Mustache-implementations).
17
18 If your goal is to design your templates so that they are compatible with those, the best way to format numbers is to have your data objects provide those formatted numbers.
19
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20 ### 1st genuine Mustache technique: NSDictionary
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21
22 Let's render the simple template:
23
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24 raw: {{ value }}
25 percent: {{ percent }}
26 decimal: {{ decimal }}
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27
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28 It's quite easy to put numbers and formatted numbers in a dictionary:
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29
30 ```objc
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31 // The raw number
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32 NSNumber *value = @0.5:
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33
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34 // NSNumberFormatter objects knows how to format numbers
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35 NSNumberFormatter *percentNumberFormatter = [[NSNumberFormatter alloc] init];
36 percentNumberFormatter.numberStyle = kCFNumberFormatterPercentStyle;
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37 NSString *percent = [numberFormatter stringFromNumber:value];
38
39 NSNumberFormatter *decimalNumberFormatter = [[NSNumberFormatter alloc] init];
40 decimalNumberFormatter.numberStyle = kCFNumberFormatterDecimalStyle;
41 NSString *decimal = [numberFormatter stringFromNumber:value];
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42
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43 // Render "raw: 0.5, percent: 50 %, decimal: 0,5"
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44 NSDictionary *dictionary = @{
45 @"value": value,
46 @"percent": percent,
47 @"decimal": decimal
48 };
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49 NSString *rendering = [template renderObject:dictionary];
50 ```
51
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52 ### 2nd genuine Mustache technique: specific properties
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53
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54 Often, data comes from your model objects, not from a hand-crafted NSDictionary.
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55
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56 In this case, the best option is to declare a category on your model object, and implement specific keys that will output the formatted numbers:
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57
58 ```objc
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59 @interface Model
60 @property float value; // the original property provided by the model
61 @end
62
63 @interface Model(GRMustache)
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64 @property (readonly) NSString *percent;
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65 @property (readonly) NSString *decimal;
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66 @end
67
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68 @implementation Model(GRMustache)
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69 - (NSString *)percent
70 {
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71 NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
72 numberFormatter.numberStyle = kCFNumberFormatterPercentStyle;
73 return [numberFormatter stringFromNumber:[NSNumber numberWithFloat:self.value]];
74 }
75
76 - (NSString *)decimal
77 {
78 NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
79 numberFormatter.numberStyle = kCFNumberFormatterDecimalStyle;
80 return [numberFormatter stringFromNumber:[NSNumber numberWithFloat:self.value]];
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81 }
82 @end
83 ```
84
85 You would then render normally:
86
87 ```objc
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88 // Render "raw: 0.5, percent: 50 %, decimal: 0,5"
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89 Model *model = ...
90 model.value = 0.5;
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91 NSString *rendering = [template renderObject:model];
92 ```
93
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94 GRMustache solution: filters
95 ----------------------------
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96
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97 **[Download the code](../../../../tree/master/Guides/sample_code/number_formatting)**
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98
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99 You may ask yourself, is it worth declaring dozens of stub properties just for formatting numbers?
100
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101 [Filters](../filters.md) are quite helpful, here. However, **it may be tedious or impossible for [other Mustache implementations](https://github.com/defunkt/mustache/wiki/Other-Mustache-implementations) to produce the same rendering.**
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102
103 So check again the genuine Mustache way, above. Or keep on reading, now that you are warned.
104
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105 Let's first rewrite our template so that it uses filters:
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106
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107 raw: {{ value }}
108 percent: {{ percent(value) }}
109 decimal: {{ decimal(value) }}
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110
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111 After we have told GRMustache how the `percent` and `decimal` filters should process their input, we will be releived from the need to prepare our data before it is rendered: no more adding of specific keys in a dictionary, no more declaration of a category on our models.
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112
113 ```objc
114 - (NSString *)render
115 {
116 /**
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117 * Our template wants to render floats in various formats: raw, or formatted
118 * as percentage, or formatted as decimal.
119 *
120 * This is typically a job for filters: we'll define the `percent` and
121 * `decimal` filters.
122 *
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123 * For now, we just have our template use them.
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124 */
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125
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126 NSString *templateString = @"raw: {{ value }}\n"
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127 @"percent: {{ percent(value) }}\n"
128 @"decimal: {{ decimal(value) }}";
129 GRMustacheTemplate *template = [GRMustacheTemplate templateFromString:templateString error:NULL];
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130
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131 /**
132 * Now we have to define those filters.
133 *
134 * Filters have to be objects that conform to the GRMustacheFilter protocol.
135 * The easiest way to build one is to use the
136 * [GRMustacheFilter filterWithBlock:] method.
137 *
138 * The formatting itself is done by our friend NSNumberFormatter.
139 */
140
141 // Build our formatters
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142
143 NSNumberFormatter *percentNumberFormatter = [[NSNumberFormatter alloc] init];
144 percentNumberFormatter.numberStyle = kCFNumberFormatterPercentStyle;
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145
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146 NSNumberFormatter *decimalNumberFormatter = [[NSNumberFormatter alloc] init];
147 decimalNumberFormatter.numberStyle = kCFNumberFormatterDecimalStyle;
148
149
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150 // Build our filters
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151
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152 id percentFilter = [GRMustacheFilter filterWithBlock:^id(id value) {
153 return [percentNumberFormatter stringFromNumber:value];
154 }];
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155
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156 id decimalFilter = [GRMustacheFilter filterWithBlock:^id(id value) {
157 return [decimalNumberFormatter stringFromNumber:value];
158 }];
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159
160
161 /**
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162 * GRMustache does not load filters from the rendered data, but from a
163 * specific filters container.
164 *
165 * We'll use a NSDictionary for storing the filters, but you can use any
166 * other KVC-compliant container.
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167 */
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168
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169 NSDictionary *filters = @{
170 @"percent": percentFilter,
171 @"decimal": decimalFilter
172 };
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173
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174
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175 /**
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176 * Prepare our data
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177 */
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178
179 Model *model = ...;
180 model.value = 0.5;
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181
182
183 /**
184 * Render "raw: 0.5, percent: 50 %, decimal: 0,5"
185 */
186
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187 return [template renderObject:model withFilters:filters];
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188 }
189 ```
190
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191 **[Download the code](../../../../tree/master/Guides/sample_code/number_formatting)**
192
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193 [up](../../../../tree/master/Guides/sample_code), [next](indexes.md)
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